Added recipe for ankle holster

Half the cost of a holster or sheath and requires survival rather than
cutting or pistol. This seemed sensible as it's a small utility
holster that can hold either a small knife or a small pistol
Made BELTED foot items not count as shoes

This means you can wear an ankle holster at the same time as footwear,
as otherwise BELTED wouldn't do anything on a foot slot.

It also means that now if you're running around wearing nothing on
your feet but socks and an ankle holster you get the "no shoes"
movement penalty.
Fixes ethanol burner crash
On hack fail, only shutdown computers next to player
Mainly for farming, show plantname when examining a square fo terrain.
Merge branch 'ethanol_burner_fix' of https://github.com/reverieAlice/Cataclysm-DDA into merge
Merge branch 'bootstrapping-bootstraps' of https://github.com/rluddy/Cataclysm-DDA into merge
Merge branch 'fix-computer-shutdown' of https://github.com/vidarsk/Cataclysm-DDA into merge
Fix typo

I think the speed's OK, but the syntax was missing something.  ;-)
Merge pull request #7878 from jeremyosborne/plant_names

Show plant names when x-amining the terrain
Merge pull request #7879 from KA101/centipede

Fix typo
Merge remote-tracking branch 'upstream/master' into issue7508_some_fixes_for_item_cutting
Begin offload of salvage code logic from outside of items to inside of items.

Idea is to have items calculate their ability to be salvaged in ideal situations. Outside operations will determine just how much of the ideal is returned (mixture of OO and structured programming).

Added a check for `item::is_salvageable()` which really just checks to see if the item does not have a NO_SALVAGE flag. Also added an `item::is_disassembleable()` which has a function name I don't like (redirects to the existing `game::get_disassemble_recipe()`).

Added `NO_SALVAGE` flags to items that were previously not meant to be `iuse::knife`d. Documented this and the UNRECOVERABLE flag I found.

Little less hard coding in valid_to_cut_up() utility function to iuse::knife.