Cleanup and fixup

Cleanup and fixup

Non-stylistic changes:
  * Add LuaDoc/LDoc support.
  * Fix `clear_objects` area size calculation.
  * Fix `clear_objects` removing player objects.
  * Fix shadowing of marker entity name with player name.
  * Make visualization functions use `swap_node`.
  * Make hidden nodes unwalkable.
  * Prevent `hide` from hiding air.
  * Make deprecated functions log to deprecated stream when called.
  * Fixed `replaceinverse` not using normalized node names.
  * Added .gitignore.
  * Bump version to 1.1.

Stylistic changes:
  * Change `x = function` to `function x`.
  * Change comment format.
  * Make  missing VoxelManip error less obnoxious.
  * Move `sort_pos` into `common.lua`, which is a required module.
  * Remove local copies of `minetest`.
  * Remove `worldedit = worldedit or {}` from modules.
  * Replace replaceinverse with an inverse argument to `replace`.
  * Added `error()`s on on invalid axes.
  * Change `wip` to `TODO`.
  * Rename `clearobjects` to `clear_objects`.
  * Remove `hollow_{sphere,dome,cylinder}` and replace them with a hollow parameter to each function.
  * Add helpers to reduce code duplication.
  * Renamed `Chat Commands.md` to `ChatCommands.md`.