introduction of armor_layers.h
slow leaks from fuel tanks
corrected for vehicle position and orientation, ensured correct amounts are dropped
reserve space for flags description, refresh warmth&enc. block properly
astyled code (not sure about spacing in brackets though). added explicit fixes for #7117
Add grammatical number support for many strings

So that grammatically awkward strings like “Upgrading bartering costs 1 points.” should be a thing of the past.

Note to developers: This has been done by calling
ngettext(singular_string_in_english, plural_string_in_english, number_to_determine_which_string_to_use)
instead of
_(some_string)
for the relevant strings. This commit touches a surprisingly large number of files.

This commit addresses all strings mentioned in GitHub issue #4649 (and some more) except item names.
Item names will (hopefully) be treated in a future commit.
Clean up IFF warning beep code
better definition of required lines for right pane
Fixes odd toilet placed
Merge fuel leaks, pluralization support, and misplaced toilet fixes.
Merge armor layering menu cleanup.

Conflicts:
	src/item.cpp