fix for BZ 860452: custom tags are now being deleted when associated entity is deleted
renamed 'CustomPermissions' into 'PermissionTagCleanup'
moved most of the modules in app/models to either models/ext or lib/ directories
fixed a syntax error under 1.8.7
Merge pull request #1451 from witlessbird/860452

fix for BZ 860452: custom tags are now being deleted when associated ent.ity is deleted