Bulgarian translation

This is the beginning of the Bulgarian translation for git.
Completed 100% - the glossary, git gui, gitk
I have additionally added some terms for the glossary plus their explanation - they are sorted alphabetically but as a next chunk in git-gui/po/glossary/git-gui-glossary.txt so that it will be easy for you to check the additional terms.
I have tried to add the best commit messages given the differences in the commit messages in previous translators' commits.
In case of a problem - I will gladly fix any issue.
Next step will be finishing the translation of the large po/git.pot file, but it is still not completed and needs more testing before merge.
Regards:
al_shopov