Add simple renaming of files

Uses a EditText view that will rename the file on pressing of "Done". There currently is no handling for
situations such as canceling the input.
Merge branch 'master' into rename
Add rename dialog fragment and context menu

Context menu will show Rename and Delete option. Renaming does not yet work properly.
Add rename and delete handling for context menu

Moved renaming from the array adapter to be handled by the context menu on long click.
Set new default file name number

Sets the new default file name starting at 1. It will increment until finding
an unused name.
Merge rename feature into master

Conflicts:
	app/src/main/AndroidManifest.xml