Amend proguardConfig to allow obfuscation in release builds.

NOTE THAT THE RELEASE SETTINGS ARE NOT HOOKED UP RIGHT NOW. Okay? Okay.
Refactor out the com.project.gutenberg.com.project.gutenberg package.

Not sure why it's there.
Add browse by title resource string.
Use app name string res instead of literal.
Use res string instead of string resource for browsing menu.