Add page about continuous integration to the Sphinx documentation
Use substitutions to facilitate job descriptions
Add scc version to the list of tools
Fix link to Trunk view of Jenkins
Fix space issue in Trunk view and add https to Github links
Create global substitution for current version development branch
Remove hard-coded version numbers in Jenkins job

As Sphinx does not allow to combine inline markup, remove the extlinks and
term links to use the global |version| substitution.
Remove URL of gretzky/howe servers
Replace 4.4 by stable for Jenkins job and restore Jenkins links
Improve scc merge program description to account for latest changes

Replace scc commands glossary by sections. Use the program and option markup
to allow references to be created in the doc.
Replace & by and
Update scc merge description of new include/exclude filters
Replace & by and

Anticipating @hflynn's comment on my PR :)
Add extra option descriptions for the merge job and give example
Replace "-stable" by "-4.4" in Jenkins jobs

NB: this change will need to be reverted once the Jenkins jobs are renamed as
stable.
Improve argparse dependency description (for Python <=2.6)
Add paragraph about Github connection (github.token, github.user)
Add note about bug/RFE reporting through Github issues
Improve description of the scc rebase command

- Add note about failing command and detached HEAD state
- Add more thorough description of the workflow of the command
- Add a couple of useful options
Fix redirected HTML links