Recyclable floor tiles

Adds the code to weld floor tiles together to make sheets, just like rods except it takes 4 tiles instead of 2 rods.
changelog.html
Merge branch 'master' of https://github.com/tgstation/-tg-station into meltablefloortiles

Conflicts:
	html/changelog.html
removed changelog.html
Merge branch 'master' of https://github.com/tgstation/-tg-station into meltablefloortiles
Welding rods/shards/floortiles now costs welderfuel
reverting last commit.

Wt.remove_fuel is 0 for a reason
Merge pull request #478 from Malkevin/meltablefloortiles

Recyclable floor tiles