continue: added support for rebase
This adds support of rebase to hg continue plan.
An independent continue logic for rebase is created
under continuerebase() function. For this a seperate
rebaseruntime object is created under the function to
handle an interrupted rebasestate.
Results of tests are shown.
Differential Revision: https://phab.mercurial-scm.org/D6646
#require docutils gettext
$ $TESTDIR/check-gendoc el
checking for parse errors