Fixes outdated mapping for the Go editor (goclipse)

Support for Go (via the ["goclipse" plugin](https://github.com/GoClipse/goclipse)) has been broken in "eclipse-color-theme" for some time, due to outdated mappings.  Quite awhile back, the plugin ID for "goclipse" changed to "`com.googlecode.goclipse.ui`", and the "`pluginKey`" elements inside of the mapping file also changed (dropping the "`_color`" suffix).

This pull request simply updates the mapping file, to reflect the new plugin ID and pluginKey names.  Discussion of the issue can be found in this "goclipse" project mailing list thread:  https://groups.google.com/forum/#!topic/goclipse/iO1wfn4ovbc.

Thanks!