Create a Gradle task to run the test server (#192)

* Create a Gradle task to run the test server

As an artifact of the old build system, the test server relies on having
the built registrar_(bin|dbg)*(\.css)?.js in place (see ConsoleUiAction
among others). As a result, we create a Gradle task that puts those
files into the correct, readable, location before running the test
server.

* Depend on assemble rather than build

* refactor gitignores

core/src/test/java/google/registry/server/RegistryTestServerMain.java

@@ -41,7 +41,7 @@ public final class RegistryTestServerMain {
   @Parameter(
       names = "--mode",
       description = "UI console debug mode. RAW allows live editing; DEBUG allows rename testing.")
-  private ConsoleDebug mode = ConsoleDebug.RAW;
+  private ConsoleDebug mode = ConsoleDebug.PRODUCTION;
 
   @Parameter(
       names = "--address",