db tweaks

- sessions autocommit
- ping_connection guards against connection timeouts
- adjusted session usage to use db.transaction when writing
Automate Explorer instance tests, fix exists()
Placement Policy for RHEV VMs.

Conflicts:
	utils/mgmt_system.py
Check for placement policy affinity

(cherry picked from commit b6e3bbe8920cace995e67abfc023dd1ccc6ecce6)
Removed time and sleeps :D
Fix Appliance.address()
This was forgotten
Merge pull request #662 from mfalesni/dbfix

This was forgotten
Merge pull request #663 from psav/time_remove

Removed time and sleeps :D
Merge pull request #661 from jkrocil/utils-appliance-update

Fix Appliance.address
Added videoer

Thanks @mfalesni for the converter help
Merge pull request #648 from psav/videoer

Added videoer
Fix flash messages for PXE CRUD
Merge pull request #665 from psav/fix_flash

Fix flash messages for PXE CRUD
soft_assert helper functions (and docs!)

Hopefully these make soft_assert more useful.
Fix force_navigate to....force_navigate
Merge pull request #668 from psav/fix_force_navigate

Fix force_navigate to....force_navigate
Merge pull request #660 from seandst/soft-asserts

soft_assert helper functions (and docs!)
Central creation of logging conf; guard agains env not having a logging conf
Merge pull request #651 from seandst/db-module-is-less-terrible

db tweaks