vcs: fix get_changesets filtering on hg repo to AND the criteria instead of OR Mercurial scmutil.revrange takes a list of filters ... and OR them. But when for example a user uses the api and sets branch name and date, he would expect to only get revisions from the provided branch. So we need to use AND when filtering. When using AND, the special handling of start_date and end_date is no longer necessary. Also add a test to check for this use case.

# requirements.txt file for use as "pip install -r requirements.txt" as a
# readthedocs compatible alternative to "pip install -e ." which is a working
# alternative to "setup.py develop" which doesn't work with Mercurial 3.7
.