Move timeToMine logic into voxel-mine

deathcap/voxel-mine@027f075ba7f82cc627fbc8d67de7c8a18c49abd5
Move item drops into registry

deathcap/voxel-harvest@ea04867046d18c784bed25d2e216436087958b27
Use new defaults for voxel-debug gui in voxel-plugins-ui, kb-bindings-ui

All modules use the same datgui instance, but now they find it themselves.
Also kb-bindings-ui uses game.buttons by default. Avoids need to explicitly
pass these options arguments.

Requires:
deathcap/voxel-plugins-ui@a33147f09083cc47a4aace5c1479dc294e7f2518
deathcap/kb-bindings-ui@187c5d9fb08f4581a6fef8d14dde43f1ff5a54ac
Move terrain block registration to voxel-land

Allows removing the 'registerDefaults' callback to voxel-registry opts

Requires deathcap/voxel-land@6c4ef7a6a7d6ab7aa0cc2f9dafeda7af4d108dcb
Switch plugin loading to be more data-driven

The plugin configuration is now represented as a data structure
instead of in code. The keys are analogous to a directory listing,
and the values can be thought of as a "configuration file" for each
plugin. (Keys, values corresponds to game, opts).
Use onDemand option from voxel-plugins

Requires deathcap/voxel-plugins@e4ffd54950b487c3cf907cf049f3ec03245b4f06
Load voxel-fly on demand instead of enabling then immediately disabling
Move creative/survival toggle to voxel-gamemode
Move thesaurus additions for wood/leaves to voxel-land

Requires deathcap/voxel-land@97f409061210f7115986c2abe9a0a1ec66975b9a
Move pickaxe tools to new voxel-pickaxe plugin

Completes this major refactor into new plugins, for now at least.
The top-level source file (index.coffee) is now finally under 200
lines, with almost everything implemented in isolated plugins.