Return 2 mismatching dictionaries to allow examination of individual PRs

Update TestUnrebasedPRs unit tests to deal with the new output
Add logic to update mismatching PR dictionary for opened and rebased PRs

Once dictionaries have been checked and missing comments have been identified,
the dictionaries run through an update_dictionary() method which goes through
each of the unfound keys in the primary PR dictionary, checks wether the PR is
open and parses the body/comments for a rebase note
Also add a parse() method to PullRequest that parses the PR body first then
parses the comments if nothing is found.
merge master -D org -I include -E exclude: PR 92 (Unrebased PRs improvement)
merge master -D org -I include -E exclude: PR 93 (Update submodules command: add first-parent log to the commit message)