Add support for customizing tree definitions

[tlammer]

There is no way to edit the tree definitions in 7.
Especially problematic when you need to add/remove a tree level.

[maxpatiiuk]

Fixed in 07b58f9
Can't add tree levels yet, but can edit all other information

[grantfitzsimmons]

Add/removing a tree level is still not at feature parity with Specify 6. I can remove Phylum when Division exists in Specify 6 where I cannot delete Phylum in 7.

[grantfitzsimmons]

Still a major point we need to solve!

[maxpatiiuk]

Regarding full name settings change, @realVinayak discovered that Specify 7 back-end already has the code for regenerating all full names, thus we can just have we can re-enable configuring full names and just call that endpointafterward.

Adding/removing tree nodes would be trickier and require seeing what sp6 does (i.e, how does it check for enforced ranks, how does it move nodes if needed)