Building base material undump script.

Based on an idea in https://github.com/peterix/dfhack/issues/119
Better way to check for the contained_items field.
Ignore Mac OS X .DS_Store files
Update Compatibility section

OS X has been supported since 0.34.11r3
Installation instructions for Homebrew
Add paths for Homebrew's gcc and g++
Added directory listing to lua api (internal category).
added mod manager and updated readme/news
Added internal lua change to NEWS
Command prompt plugin with docs and readme patch.
Cmake fix
Make siege engine debug markings toggleable via lua.

Also check that the tile actually exists to avoid crashes.
Squash uninitialized variable warnings.
Switch to the new random number generator class.
Compute quality of siege engines and use it to extend firing range.

Since parts aren't there until it is built, it requires checking that.
Rewrite aiming error code to account for distance and engine quality.

Now the error is simulated by using an approximate normal distribution.
Always shatter glass items within bins thrown by a catapult.

The glass materials have impact strength copied from compression
strength, so the items had 1/5 chance to survive without damage.
Since glass is infinite, it makes sense to make it single-use.
Removed rendermax from NEWS.
Added an output stream, now response is visible in same window. Also added a way to start prompt pre-filled.
It's nice to bind it to e.g. ctrl-shift-o "command-prompt :lua"
New plugin: building-hacks. Allows workshops to block liquids and consume mechanical power, connect to machines.
Added animation and on update callback.