Fix .classpath to make jgit easily runnable from inside eclipse

When running jgit from inside Eclipse (e.g. rightclick on project
org.eclipse.jgit.pgm and select Run as->Java application) no commands
are found. This is because the commands are loaded from a resource file
/META-INF/services/org.eclipse.jgit.pgm.TextBuiltin and this file is
not anymore on the classpath.
I fixed this by modifying .classpath to contain the META-INF directory.

Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>