Since the upcoming Spigot 1.13 is turning into a pretty major update with many under-the-hood changes, I'll probably drop support for 1.11.x and below. Old versions will remain available.
FIXED - many issues for sub 1.12.x server that arose from adding logger plugins support
FIXED - entering non-creative world with creative mode enabled didn't switch inventories (thanks @muhyo )
FIXED - destroying a survival-placed item frame containing a creative-placed item dropped the item (thanks @muhyo )
FIXED - creative players could build creatures in certain circumstances (thanks @andris155 )