Project flags should be reset if the list of repositories to export is changed or a new fork is found

[philipstarkey]

We have a lot of flags (like fork_search_complete or bitbucket_hg_download_complete) that need to be reset if new repositories are added to the list of repositories to export. For example, if a repository is added/removed from the list of repositories then we need to rescan for forks (because that step overwrites the list of repositories to export to which forks were added at a different step).

There are other flags that could also be reset.