Added creation time

* Getter and setter for files and folders
* A way to determine if a file system supports creation dates
* WebDav compliant implementation in jackrabbit-adapter
* Tests

main/filesystem-api/src/main/java/org/cryptomator/filesystem/FileSystem.java

@@ -23,4 +23,8 @@ public interface FileSystem extends Folder {
 		return Optional.empty();
 	}
 
+	default boolean supports(FileSystemFeature feature) {
+		return false;
+	}
+
 }

main/filesystem-api/src/main/java/org/cryptomator/filesystem/FileSystemFeature.java

@@ -0,0 +1,5 @@
+package org.cryptomator.filesystem;
+
+public enum FileSystemFeature {
+	CREATION_TIME_FEATURE
+}

main/filesystem-api/src/main/java/org/cryptomator/filesystem/Folder.java

@@ -7,6 +7,7 @@ package org.cryptomator.filesystem;
 
 import java.io.IOException;
 import java.io.UncheckedIOException;
+import java.time.Instant;
 import java.util.stream.Stream;
 
 /**
@@ -148,4 +149,18 @@ public interface Folder extends Node {
 		}
 	}
 
+	/**
+	 * <p>
+	 * Sets the creation time of the folder.
+	 * <p>
+	 * Setting the creation time may not be supported by all {@link FileSystem FileSystems}. If the {@code FileSystem} this {@code Folder} belongs to does not support the
+	 * {@link FileSystemFeature#CREATION_TIME_FEATURE} the behavior of this method is unspecified.
+	 * 
+	 * @param instant the time to set as creation time
+	 * @see FileSystem#supports(Class)
+	 */
+	default void setCreationTime(Instant instant) throws UncheckedIOException {
+		throw new UncheckedIOException(new IOException("CreationTime not supported"));
+	}
+
 }

main/filesystem-api/src/main/java/org/cryptomator/filesystem/Node.java

@@ -5,6 +5,7 @@
  ******************************************************************************/
 package org.cryptomator.filesystem;
 
+import java.io.IOException;
 import java.io.UncheckedIOException;
 import java.time.Instant;
 import java.util.Optional;
@@ -33,6 +34,20 @@ public interface Node {
 
 	Instant lastModified() throws UncheckedIOException;
 
+	/**
+	 * <p>
+	 * Determines the creation time of this node.
+	 * <p>
+	 * Setting the creation time may not be supported by all {@link FileSystem FileSystems}. If the {@code FileSystem} this {@code Node} belongs to does not support the
+	 * {@link FileSystemFeature#CREATION_TIME_FEATURE} the behavior of this method is unspecified.
+	 * 
+	 * @returns the creation time of the file.
+	 * @see FileSystem#supports(Class)
+	 */
+	default Instant creationTime() throws UncheckedIOException {
+		throw new UncheckedIOException(new IOException("CreationTime not supported"));
+	}
+
 	/**
 	 * @return the {@link FileSystem} this Node belongs to
 	 */

main/filesystem-api/src/main/java/org/cryptomator/filesystem/WritableFile.java

@@ -24,6 +24,20 @@ public interface WritableFile extends WritableByteChannel {
 
 	void setLastModified(Instant instant) throws UncheckedIOException;
 
+	/**
+	 * <p>
+	 * Sets the creation time of the file.
+	 * <p>
+	 * Setting the creation time may not be supported by all {@link FileSystem FileSystems}. If the {@code FileSystem} this {@code WritableFile} belongs to does not support the
+	 * {@link FileSystemFeature#CREATION_TIME_FEATURE} the behavior of this method is unspecified.
+	 * 
+	 * @param instant the time to set as creation time
+	 * @see FileSystem#supports(Class)
+	 */
+	default void setCreationTime(Instant instant) throws UncheckedIOException {
+		throw new UncheckedIOException(new IOException("CreationTime not supported"));
+	}
+
 	/**
 	 * <p>
 	 * Deletes this file from the file system.

main/filesystem-api/src/main/java/org/cryptomator/filesystem/delegating/DelegatingFolder.java

@@ -9,6 +9,7 @@
 package org.cryptomator.filesystem.delegating;
 
 import java.io.UncheckedIOException;
+import java.time.Instant;
 import java.util.Optional;
 import java.util.stream.Stream;
 
@@ -90,4 +91,9 @@ public abstract class DelegatingFolder<R extends DelegatingReadableFile, W exten
 		}
 	}
 
+	@Override
+	public void setCreationTime(Instant instant) throws UncheckedIOException {
+		delegate.setCreationTime(instant);
+	}
+
 }

main/filesystem-api/src/main/java/org/cryptomator/filesystem/delegating/DelegatingNode.java

@@ -39,6 +39,11 @@ abstract class DelegatingNode<T extends Node> implements Node {
 		return delegate.lastModified();
 	}
 
+	@Override
+	public Instant creationTime() throws UncheckedIOException {
+		return delegate.creationTime();
+	}
+
 	@Override
 	public int hashCode() {
 		return delegate.hashCode();

main/filesystem-api/src/main/java/org/cryptomator/filesystem/delegating/DelegatingWritableFile.java

@@ -67,4 +67,9 @@ public class DelegatingWritableFile implements WritableFile {
 		delegate.close();
 	}
 
+	@Override
+	public void setCreationTime(Instant instant) throws UncheckedIOException {
+		delegate.setCreationTime(instant);
+	}
+
 }