Fix issue2551029 (Jinja2 template install error) by deleting config.ini from all templates. Looks like classic and minimal never included a config.ini. Presence of config.ini stopped 'roundup-admin install' from generating an up to date config.ini. Created special option class for backend database. Comment now uses roundup.backend.list_backends to give user indication of valid values. Also we now get an error if user specifies invalid backend. Moved backend setting to top or [rdbms] section. It is the most important thing in there and if set to anydbm (or some other non-rdbm) the rest of the settings can be ignored. Change rdbms config section comment to indicate that the backend setting was used by other database backends. (e.g. if set to anydbm).

recursive-include share *
recursive-include roundup *.*
recursive-include frontends *.*
recursive-include scripts *.* *-*
recursive-include tools *.* base64
recursive-include test *.py *.txt
recursive-include doc *.html *.png *.txt *.css *.example
recursive-include detectors *.py README.txt
global-exclude *.pyc *.pyo .DS_Store *.orig *.rej *~ \#*
include run_tests.py demo.py *.txt
include doc/conf.py doc/roundup-favicon.ico
exclude doc/security.txt
include locale/*.po locale/*.mo locale/roundup.pot