Issue 1571 - Options group strings and limits

[Issue 1571](http://code.google.com/p/ankidroid/issues/detail?id=1571)

- Updated some strings to match the desktop client.
- Fixed an option using the wrong units 
- Added limits to the input text length.
- Disabled the add/remove options group item for now since it doesn't do anything yet.

The desktop client also has minimum and maximum values for most of these which we aren't checking for. I'll do that next.