provision_civicrm 6.x-2.2

#2472607: Fails to install civicrm 4.6.1 and up (No such file or directory civicrm.php:43)
#2411137: Drush 7 compatibility
#2364871: Error installing civicrm in /profiles folder
#1485920: Install CiviCRM with the same default language as Drupal
Verify: only change permissions on 'dynamic' directory if it exists (new since civicrm 4.5).
Add files/civicrm/dynamic, for CiviCRM 4.5.
_provision_civicrm_upgradedb: show the upgrade output as a warning. Most civicrm upgrades show instructions that the user should read.
Update and fixurls: use functions from civicrm.drush.inc instead of duplicating the code (now possible since we use the version-specific civicrm.
A lot of code cleanups.
README.txt: provision_civicrm 6.x-2.x requires hosting_civicrm.