checker: raise the exception after bad_exit()

checker: move hg calls to separate functions, check config['scm']

models: revs are not unique, can be nulls Revision numbers can change depending on --branch or --rev for hg clone.

incoming: job started/finished metadata lines are not in any task

models: manual_upsert() to create new instances or update existing

models: use a simple heuristic to pick HgwebAdapter

viewer: move project name closed to the check result on /

viewer: remove Check.get_url() method for not being very useful

viewer: join change table in check handler for performance reasons

adapters: add hgweb hosting adapter