* add deco groups and decos; set default deco for block playout
* use block playout default deco for watermark
* add deco templates, groups and deco template editor
* associate deco template with playout template
* use deco template item watermark for playback
* update changelog for decos
* schedule blocks in order
* block minutes must be multiple of 15
* improve block minutes entry, validation and display
* confirm deleting blocks and block groups
* confirm deleting templates and template groups
* skip unchanged blocks in playout