Active mutation changeover

Some mutations seem to work better as active ones.  Let's get things
moving.
Tweaks & bugfix

This teaks a few things, adds a very important TODO (active mutations
are Exploitable without it) and fixes #8959.
Carnivore nutrition

KarmaChimera and Grizzlyadamz made a good point on the IRC: tough to get
Healthy food for Carnivores.

This helps take the edge off total vitamin dependence, since obligate
carnivores in the wild seem to live reasonably non-diseased lives.
Allow random descriptions for all item types.

Moves the snippet_category into the itype class and removes the it_stationary class as it is not needed anymore.
Random description are used when the item type has a snippet category.
Allow random descriptions to be specified in the item definition:

Instead of having separate entries, the snippet category is automatically created and filled with the given snippets.

Also adds check for snippet category to exist.
Add translation for snippet text inside of item definitions:
Professions return the combined item list including gender specific and gender-neutral items.
Allow professions to specific the description of the starting items.
Adds items for making cement

Adds limestone shard, limestone, quicklime, sand and cement.
Adds recipes for cement making

Adds recipes for making quicklime out of limestone and cement out of quicklime and sand.
Adds limestone shard deconstruction

Adds the recipe for deconstructing limestone shard into limestone.
Adds drops for limestone shard and sand

Makes sand drop in field (rare than rocks) and limestone shards drop in mine storage (equally often as rocks).
Updates facility items

Updated prices and materials of new facility items (limestone/quicklime/sand/cement)
Update melee.json
Snippet library: added an optional id to snippets.

Uses that id instead of the original text in the profession item list.
Adds a new warehouse building

Just a warehouse filled with a lot of crates and a possible flatbed truck in the middle. Not yet linked to anything.
Based on house_rv.json by John-Candlebury.
Adds items on the floor and in crates

Adding items to make the building seem cluttered.
Makes the proper vehicle spawn

Thanks for pointing it out !
Typo fix

Fixes typo in material_cement description
Adds warehouse to overmap

Adds warehouse to overmap terrain and gives it light blue "W" as a symbol, with "small warehouse" as the name for the tile.