More punctuation fixes.
Formatting fix.
Apply field effects to npcs as well.

Change map::step_in_field to use a player parameter (can be either the player character or an npc).
Change map::mon_in_field to take a monster reference.

Both functions use the position of the creature instead of having that as separate parameters.
Add wrapper map::creature_in_field which is usable for any creature and simply forwards to the appropriate function.

Use player::add_msg_* when showing messages for player/npc with additional messages for npcs.

Add call to creature_in_field for npcs when they move similar to what is done for monsters.
Make npcs aware of dangerous fields and let them act.
Typo fixes: armor
Changed "signalling" (UK) to "signaling" (US).
Typo fixes: bionics.
Downcased generic names of drugs.
Replaced "litre" (UK) with "liter" (US).
Typo fix: handloaded ammo.
Typo fixes and Amerifixes: melee items.
Typo fixes and Amerifixes: ranged weapons.
Punctuation fix.
Capitalization fix.
Typo fixes: lab notes.
Typo fixes and Amerifixes: monsters.
Typo fixes: mutations.
Changed "travelled" (UK) to "traveled" (US).
Typo fixes: tutorial.
Use "saber" and "fiber" consistently (in user-visible text).