[manifest] Remove bootstrap from file list, add other cfg files

MANIFEST.in

-include LICENSE.AGPL README.rst bootstrap-buildout.py buildout.cfg
+include LICENSE.AGPL README.rst buildout.cfg common.cfg release.cfg
 recursive-include beat/web *.css *.png *.gif *.svg *.ico *.js *.html *.rst *.txt
 recursive-include doc conf.py *.rst *.png *.svg *.ico *.pdf
 recursive-include beat/web/backend/environments/default/bin execute describe