Bug 508905: Change File.canWrite to Files.isWritable for p2 Droplets.

For compatibility with Windows, use java.nio.Files.isWritable(Path)
instead of java.io.File.canWrite(). This is due to the fact that
canWrite always returns true for directories on Windows.

- Enable all tests disabled on Windows by 416b782
- Introduce reallyReadOnly/removeReallyReadonly functions that operate
  recursively on a directory (like chmod -R on linux) since certain test
  cases require this

Change-Id: I615dfdef60e4abd23c34602bd324c307325e00d4
Signed-off-by: Roland Grunberg <rgrunber@redhat.com>
8 files changed