Creative mode support

[dawnraider]

I would like to make creative mode an officially supported mode for the community edition, and as such feedback and bug reports about creative mode will be addressed.

At the immediate moment I am tackling the following issues regarding creative mode:
- Removing mechanical restrictions on creative mode worlds in things such as villager trading
- Adding missing items to the creative menu
- Fixing issues using pick block

Additionally I'd like to eventually look at improving organization for the tabs, and adding support for addons to add their own tabs.

[hawk]

Not sure weather to post this here or on Github , but the Vessel of the Dragon is missing from the creative menu

[dawnraider]

Ok I'll take a look and get that fixed. Thanks :)

[hawk]

Witch wart and mysterious gland, as well. :)

[hawk]

And the bloody chopping block (clean one is there).

Sorry these are piecemeal! I'm just going back through villager trading in my creative world since it's been a few years since I've done it. I'm just posting them as I come across them.

[dawnraider]

Vessel of the dragon, witch wart, and mysterious glands have been added. Bloody chopping blocks are present for me in CE so I suspect that is an issue with deco since it touches the class used for chopping blocks.