Make the massager using singleton and remove all uses of $GLOBAlS

Also load the instances for the acp
Merge pull request #89 from JN-Jones/singleton

Make the massager using singleton and remove all uses of $GLOBALS
Added missing PHPDoc and braces.
Fix #78.
Fix #86.
Fixed #84.
Working on #88.
Added checking for user alert type disablement for #88 to AlertManager.
Added management for can be user disabled to admin area.
Fixed #88.
Fixed #85.
Fixed #90 and using modal to show alerts rather than buggy dropdown which had theme conflicts.
Changing code column to VARCHAR(100).
Fixed checking of unread messages for CSS class.
Fixed #67 (hopefully).
Fixed issues with PM ID for #67.
Added simple clear all alerts link to modal for #73.
Added confirmation to clear alerts in modal via JavaScript, same as UCP.
Fixed #91 and cleaned up CSS.
Using format_avatar to format avatars.