Refactored filesystem api

* Removed Readable- and WritableBytes
** Replaced with Readable-/WritableByteChannel
** Methods now integrated in Readable- and WritableFile
** Replaced positioned read/write by method to set the position

main/filesystem-nio/src/main/java/org/cryptomator/filesystem/nio/NioFile.java

@@ -42,11 +42,17 @@ class NioFile extends NioNode implements File {
 	private class ReadableView implements ReadableFile {
 
 		@Override
-		public void read(ByteBuffer target) throws UncheckedIOException {
+		public int read(ByteBuffer target) throws UncheckedIOException {
+			return -1;
 		}
 
 		@Override
-		public void read(ByteBuffer target, long position) throws UncheckedIOException {
+		public boolean isOpen() {
+			return false;
+		}
+
+		@Override
+		public void position(long position) throws UncheckedIOException {
 		}
 
 		@Override
@@ -62,11 +68,17 @@ class NioFile extends NioNode implements File {
 	private class WritableView implements WritableFile {
 
 		@Override
-		public void write(ByteBuffer source) throws UncheckedIOException {
+		public int write(ByteBuffer source) throws UncheckedIOException {
+			return -1;
 		}
 
 		@Override
-		public void write(ByteBuffer source, int position) throws UncheckedIOException {
+		public boolean isOpen() {
+			return false;
+		}
+
+		@Override
+		public void position(long position) throws UncheckedIOException {
 		}
 
 		@Override

main/filesystem-nio/src/test/java/org/cryptomator/filesystem/nio/NioFolderTest.java

@@ -1,7 +1,7 @@
 package org.cryptomator.filesystem.nio;
 
 import static java.util.stream.Collectors.toList;
-import static org.cryptomator.commons.test.matcher.ContainsMatcher.containsInAnyOrder;
+import static org.cryptomator.common.test.matcher.ContainsMatcher.containsInAnyOrder;
 import static org.cryptomator.filesystem.FolderCreateMode.FAIL_IF_PARENT_IS_MISSING;
 import static org.cryptomator.filesystem.FolderCreateMode.INCLUDING_PARENTS;
 import static org.cryptomator.filesystem.nio.FilesystemSetupUtils.emptyFilesystem;

main/filesystem-nio/src/test/java/org/cryptomator/filesystem/nio/NioNodeMatcher.java

@@ -2,7 +2,7 @@ package org.cryptomator.filesystem.nio;
 
 import static org.hamcrest.CoreMatchers.equalTo;
 
-import org.cryptomator.commons.test.matcher.PropertyMatcher;
+import org.cryptomator.common.test.matcher.PropertyMatcher;
 import org.cryptomator.filesystem.File;
 import org.cryptomator.filesystem.Folder;
 import org.hamcrest.Matcher;