When building, compile .strings files in resources/ into binary plist instead of copying them verbatim.

Related to https://groups.google.com/d/msg/rubymotion/dTMzDPp2IUo/IgTplWdYt-YJ.

The commit compiles *every* .strings file within resources/ and other inner directories, not checking only for en.lproj, etc. I'm not sure if this is a correct assumption.