Fixes pipe bug.
Issue https://github.com/tgstation/-tg-station/issues/1669 and its duplicate https://github.com/tgstation/-tg-station/issues/1099
Fixes the HE pipes.
 * Simple animals will now consider invisibility when attacking and choosing targets.
 * Renamed SA_attackable to CanAttack(). Moved relevant code into there. Should make mobs more responsive with their targets.
* AIs can no longer intercept messages randomly. Instead they can use the Message Monitor by getting their cyborg to get the keypass.
* The Captain's PDA no longer starts off, instead their PDA is detonation proof.
 * Made wet floors use a static overlay.
 * Standardized the wet floor code, it is now called MakeSlippery(var/wet_setting)
 * Added the wet floor static overlay, which is just a single frame of the usual animation.
 * Made the floor randomly dry (by a few seconds apart), for visual effect.
Re-added mode.txt. Added it to the ignore list.
Stops people from spamming the "summon narsie" rune to summon him more than once. Fixes #1680.
You can no longer summon narsie more than once, with different runes in different locations.
The narsie rune will move any current narsies, if one exists already.
Merge pull request #1792 from Giacom/PDA_tweak

AIs can no longer intercept messages randomly. Captain PDA no longer starts off.
Merge pull request #1780 from Giacom/simple_animal_invis

Simple animals will now consider invisibility when attacking and choosing targets.
Merge pull request #1793 from Giacom/wet_static_overlay

Made wet floors use a static overlay.
fixed narsy gender but shh don't tell gia
Merge branch 'master' of https://github.com/tgstation/-tg-station into narsie_spam
Merge pull request #1799 from Giacom/readd_mode

Re-added mode.txt. Added it to the ignore list.
Merge pull request #1777 from adrix89/pipeFix

Fixes pipe bug.