Add-ons Standard Library by Xon 1.20.1

• Fix accidental hard XF2.2 requirement. Take #2

• Fix accidental hard XF2.2 requirement

Note; The 1.18.x branch will be the last branch to support XenForo 2.1.x

• Deprecate getContentPermissions function, as the 2nd string argument was not actually used, with a replacement function getPerContentPermissions added.
• Add \SV\StandardLib\Helper::isAddOnActive() helper function. Similar to \XF::isAddonActive(), except it understands version strings
• Shim template funciton is_addon_active code to understand version strings