Make sure protocol is in environ['url_scheme'] (fixes #599)

Instead of forcing the scheme, we could also let
paste.deploy.config.PrefixMiddleware decide which protocol to set,
according to `X-FORWARDED-PROTO` and similar HTTP headers. However this
would require to configure the reverse proxy to actively pass that stuff
around.
Allow empty watch div to be skipped
Remove redundant routing entry
Allow all user related urls to be in an instance
Allow multiple base groups in initial permission configuration

Conflicts:
	src/adhocracy/lib/install.py
Allow watch.create without instance join by default
mv notifications from lib.events to model
move migration after rebase
resolve circular imports
add database sink to notification pipeline
define event type mappings
create event type sets
distinguish between event type and notification type
allow different event pager row types
add class ${pager.name}_pager to all named pagers
new css for events pager
rename sort_options to autoreload
nicer vote to html
new profile templates and controllers
add icons