Update server service help.
Improve filter type explanation in scc merge section

- Expose both forms of inclusion/exclusion by PR number
- Expose inclusion/exclusion of submodule PRs by number
Add section about scc travis-merge command

- Expose the comment parsing strategy to define the include filters
Pluralize filters as suggested by Mark
Replace Pull Request by its abbreviation
merge develop -D org -I include -E exclude: PR 450 (omero: Python 2.6 is the minimum supported version)
merge develop -D org -I include -E exclude: PR 479 (Update Windows service docs (see #11448) (rebased onto develop))
merge develop -D org -I include -E exclude: PR 481 (Travis merge documentation (rebased onto develop))