Add --shallow and --remote descriptions to the scc-scripts page
Add section about scc update-submodules command
Add section about scc unrebased-prs command
Improve usage of versionadded/versionchanged markup for 0.3.10

Add note about the rebased-to/from comments in scc rebase section
Fix formatting as per Helen's suggestion

Use :option: markup to render double-dashed comment lines in scc unrebased-prs
Fix erroneous rebased-to comment line as reported by Blazej
Merge pull request #475 from sbesson/rebased/develop/scc_0.3.10

Scc 0.3.10 (rebased onto develop)