Remove remenants of mob code

Since minetest has no mobs within the core anymore, I suppose these
settings and code should go. Any mod that uses `minetest.setting_getbool`
will work with no problem since the default return value is `false`.
Remove m_ext_ptr in GUIFormSpecMenu, replaced by refcount mechanism
Add NodeResolver and clean up node name -> content ID resolution system
Add support for eased 3d noise
Change license of noise implementation to Simplified BSD
Prevent invalid memory access under failure conditions
Add NodeResolver documentation

Set content to fallback on AddNode failure
Consider node list requests with no results as failed
Add notice when only minimal is installed
Fix #1733: An unhandled exception occurred: GetPeer: Peer not found (possible timeout)
Fix various indentation issues
Refactor decoration-related code

Split up ModApiMapgen::l_register_decoration()
Define and make use of CONTAINS() and ARRLEN() macros
Added names colours and refactored parseColorString()
Add option to enable mesh caching, add wallmounted for meshes.
Fix bug introduced by me (Zeno)
Check minetest.hud_change() parameters on conversion (Fix #1714)
mapgen: Resolve nodes in ctor rather than makeChunk
Fix uninitialized variable warning
Fix erroneous lua_pop parameter
Split up mapgen.cpp
Refactor the_game() to make it more understandable and maintainable.

The following is a record of 31 commits before squashing:

Revert "Remove m_ext_ptr in GUIFormSpecMenu, replaced by refcount mechanism"

This reverts commit b49e5cfc7013cef7e9af79d17e04f7e7e4c377d4.

Basic reformatting with astyle
-- additional formatting will be modified, manually, as the need for it is encountered

Start "outlining" what a MinetestApp class might look like

Add MinetestApp::shutdown()

Converted class member functions to camelCase and created protos for new functions

First stage of connect to server done

Add get itemdefs/nodedefs/media code

Init clouds, camera, sky, init GUI, HUD

Input handling

Client events, camera, sound, draw

Fix wield hand getting stuck digging and add debug text back

Fix FPS

Added profiler graph back

Fix FPS issue
Need to work out what went wrong and clean up the copy/paste stuff

Annotate

Various:
Rewrote limitFps()
Limited scope of some variables

Jitter calcs

Reduce scope of objects

Move some stuff out of ::run and minor formatting cleanup

Scope reduction

Function splits

Removed old (broken) limitFps()

Added exception handling back

Fixed some formatting

Reverted commented out unit tests (uncommented them)

Slow clouds down on loading and media screens so the behaviour is like the original the_game()

Formatting/style (no functional changes)

Manually reapply upstream b49e5cf: Remove m_ext_ptr in GUIFormSpecMenu, replaced by refcount mechanism

Fixed silly errors on my part
Minor formatting cleanups

Removed strange differentiation in FPS limiting when loading
FPS limiting was done differently if cloud_menu_background was true, which does not make sense

Cleaning up

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