Move Msf::DBManager#migrate(d) to module

[#50179803]

Move Msf::DBManager#migrate and the migrated attribute to
Msf::DBManager::Migration module to lower complexity of db_manager.rb
and in preparation for more migration related code on this branch.
Merge branch 'master' into bug/migrations
Reset column information after running migrations

[#50179803]
[SeeRM #7967]
[SeeRM #7870]

Because metasploit-framework runs migrations with the same process and
with the same connection as it later accesses the database, the column
information can become cached prematurely and be incorrect by the end of
the migrations.  Fix the bad cache by automatically resetting the column
information for all model classes after the migrations have run.
Merge pull request #1852 from limhoff-r7/bug/migrations

[Delivers #50179803]
Axe a bunch of svn cruft

So long, $Id$ and $Revision$.
Rename CmdStager* classes in Rex

e.g.: CmdStagerBase --> CmdStager::Base

Makes classes match up with filenames
Break Job out into its own file
Hmm, copyright date hasn't been updated in a while
Remove old xor encoder unit tests

Superceded by recent specs
Add minimal specs for some stuff in rex/proto/http
Refactor CmdStager