Add git administrators section in Git service

Change-Id: Iee399cdc1d2327d3e0a46788e2498613b5ca8951
Remove project_admins from selectbox

* We keep the default value in permissions_values table
  in order to have the same behaviour for this access right
  as the others in Tuleap

Change-Id: I12711df4f717ec5814004e7f9536e86ed63c56d6
Forge upgrade : Add project_admins git admins for all exsiting project

Change-Id: I94628189af64ad3429164916aaca853efb332c8e
Save groups selected in DB from selectbox

Change-Id: I8c0f7232b7f3162b845bc2277f58f516816ceedd
git admin permissions are duplicated

Change-Id: Ibb75cf1224463aa8d8aefd22161d9827c50533ad
project_admins are now PLUGIN_GIT_ADMIN by default when plugin git is installed

* After the installation, the usergroup project_admins is
  automatically granted to PLUGIN_GIT_ADMIN in project 100.
  With duplication, this permission will be duplicated into all
  other projects.

Change-Id: I780e781fbb8ae8f43d0b28ce28a5401106ba0d57
Have a smarter permission validation

Change-Id: I644a91420e847a7c612cebe28316b10ca752f635
Add GitPermissionsManage and refactor git admin verif

Change-Id: I893843f3824ca1ed1ad48b4f1d4473d3bf2c2663
Removed all_users and registered_users from selectbox

Change-Id: Ibd3124111b728291434fa265f15da40cb7c63fd2
Merge remote-tracking branch 'gerrit/5870_git_admin_permissions' into HEAD

* gerrit/5870_git_admin_permissions:
  Removed all_users and registered_users from selectbox
  Add GitPermissionsManage and refactor git admin verif
  Have a smarter permission validation
  project_admins are now PLUGIN_GIT_ADMIN by default when plugin git is installed
  git admin permissions are duplicated
  Save groups selected in DB from selectbox
  Forge upgrade : Add project_admins git admins for all exsiting project
  Remove project_admins from selectbox
  Add git administrators section in Git service

Conflicts:
	src/common/autoload.php

Change-Id: Ia65c0b09f04e5070a09bb6851926c8b9281370bd
This is Tuleap 6.9.99.44

Change-Id: Ie07bf73252d44b270e5ada51f42d286cabc7d7ed