Don't ignore essential Android Eclipse project and classpath files.

I put a pretty thorough description of why these files shouldn't be ignored in the commit message. This is probably hitting a lot of people hard with the [ADT version 22 update](http://stackoverflow.com/questions/16603002/classnotfoundexception-on-androidannotations-generated-classes-since-update-to-a).

The original committer thought that these files are environment-specific, especially as it comes to file paths of libraries imported manually into a project. Eclipse handles relative file paths in Windows, MacOS, and Linux just fine. In the case of a manual file path such as "/dev/mylib/mylib.jar", this is not standard as most classpaths should be relative to a project. If they aren't relative, well then such paths shouldn't be shareable as in a shared git repository.

Fixes #495.