Spruce up Cipher+NativeFileTest

* Sync testWriteSkipWrite
* Uncomment testMkdirRename
* Test for directory contents in testMkdirRename
Remove outdated test and add testRenameToExisting

The old test was cruft from when renaming dirs didn't work.
Fix testMountKeyWithBadPassword so it does what it purports to do.
Integrate IOCipherThreadTest submitted by Aaron Huttner
Add some more features to ThreadTest
Add reset button to test.

There's a bug that prevents the strobing from starting automatically,
but I don't want to spend the time tracking this down (this is a simple
test case afterall), so you might need to manually start the strobing.
make the app debuggable
Update .gitignore
The append test now verifies that the data was written correctly