Moved some code out of cata_tiles::load_tileset and to somewher ebefore that function is called.

The function called (probably) multiple times now and the moved code needs only to be called once.
Extracted some common code into a separate function.

That function does now the range checking of fg/bg
Add ability to load tiles that a re going to be used as ASCII replacement.

Changed the retro tileset to include ASCII tiles.
Add ascii fallback for furniture/terrain/monsters/fields/traps/items

Fixes a bug for the roation certain multitile definition from ascii
Add ascii fallback for vehicle parts

Load certain LINE_XOXX_* ascii values differently
Make cata_tiles::tile_values a std::vector.

It was already used as vector anyway.
Add the standard headres as their content is used. It worked so far out of pure luck, the other headers included them for us.
Transform category parameter of cata_tiles::draw_from_id_string to an enum.

There are only a handful of different categories. A string is not needed.
Make id parameter of cata_tiles::draw_from_id_string a const reference.

Ther eis simply no need to copy that string all the time.
Make subcategory parameter of cata_tiles::draw_from_id_string a const reference

Use a static empty string to avoid creating new strings each time.
Corrected the colors in the tileset config.

Thanks to Abalieno for pointing me to the correct values.
Allow tilesets to define a transparency color.
Raised water's cost
Make the default value for background and foreground tile -1.
Modifies foraging rates, brings PER into calculations
Merge branch 'master' of https://github.com/CleverRaven/Cataclysm-DDA into forage
Updates prices for alcohol

Also fixes spiced mead's weight
Reduce barrel prices to 0

Some stuff might generate in them (plus a 30 gallon barrel is not worth
5000 bucks), so until someone gives them a proper price, they shoul be
worth 0 like other containers.
Adds (drink) note

By Wuzzy's & Rivet's request, at #6494.
Readd double head damage until we figure out if intended behavior or not
More slime mutations-in-progress

Taking time out to merge that fix.