Establish a vocabulary and use it consistently

[kpreid]

The code is inconsistent in these issues:

• ‘blockset’ or ‘blockSet’? Fixed
• Is the element of a world's data array a ‘block’, a ‘blockID’, or a ‘value’?
• Is the element of a world's ‘subdata’ or ‘subData’ array a ‘subdata’ or a ‘subdatum’?

There should be a glossary which defines and spells such words, as well as explaining e.g. the difference between a block and a block type.

[kpreid]

I have created a wiki page with this information, Glossary, but it should eventually be incorporated into the repository as user and developer documentation (accessible in-game, in particular).

The code has not yet been made consistent.

[kpreid]

• blockSet eliminated in bfa69897333d53bf8c8e83ed0b273529d926c4a0.
• BlockSet eliminated in c3875f29341dd35a617e3762df26b15deb761839, except for serialization.