Implement submitted changeset posting for Perforce.
This change implements posting for submitted changesets in Perforce. In order

to do this, we fetch the filelog between those revisions, which will give us a

list of every change to every file within those revisions. This is then

processed to accumulate changes together. At the end of this, for each file,

we'll have one of four operations: add, delete, edit, or move. Move operations

can also include edits. This is a little bit complicated to track moves within

the revision range. Just diffing the two trees would handle adds, deletes, and

edits, but not moved files.

Ran unit tests
Posted a variety of revision range changes which included all four of the

  overall change types.