Update for power code to remove some bugs and fix some functionality
Functionality
========
*Cables can now be placed across each other and not connect, just like cables placed in the map editor.
*Alternately by leaving a "node" or "dot" in both cables you can have these cables connect

Bugs Fixed
=======
*Unconnected cable networks which share the same powernet and power are no longer created when adding cable to nodes or removing nodes on top of smooth cable

Code changes:
==========
*Adds denode proc that should be called when a wire is added to causing it to no longer be a "node" (i.e. terminates in the centre of the turf)
*Adds propagate_network proc that traverses the graph adding every cable to a new network while removing the old one
*Adds call to denode in the cable_join proc
*Fixes mergeConnectedNetworksOnTurf() to only connect cables that are both nodes
*Adds a get_marked_connections() proc to cable which finds all edges connected to it's endpoints regardless of whether they have a powernet(as opposed to get_connections())
clarified a comment
creating a get_marked_connections method for machines that doesnt check for powernet==null
making propagate_network non recursive
Fixed some container escape issues
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.
Fixed being able to escape moving lockers
Fix for being unable to unwrench vents
Attacking unanchored windows truns them into stacks of glass
removing unnecessary "/" from variant declaration
* 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.
 * Rewrote the explosion sound to be more optimized and to be more dynamic.

Explosions that are close to you play the usual sound.
Explosions which are far away will play explosionfar.ogg but with volume differences depending on the distance.
Max cap bombs will play explosionfar.ogg for half of the station (140 tiles).
Explosion sounds will have panning, so stereo users will be able to tell the direction that the sound came from.
Small bombs will play much less than max cap bombs, and be quieter.
The narsie rune will move any current narsies, if one exists already.
Refactored big package attack code
Reformatted the way objects and items structure their description text, added the little object "icon" everyone seems to be using.

Added superclass invoke for the arcane tome

Added superclass invoke to light switches, removed it's (unused) description.

FLightswitch description repetition derp

examine superclass invoke for gas flow meter, space heater, fire extinguishers, grenades/IEDs, fancy boxes and welder. Changed description for welder and fire extinguisher to show their content in a similar style.

Fixed tank, linen bins and janicart description, and added welder of previous commit (forgot to commit it)

REMOVED icon in mop_bucket description (now provided by item class).
REMOVED unused examine() override in clothing/gloves
REMOVED custom examine() for glass/rag
CHANGED using examine superclass on paperwork/paperbin, removed redundant description code
CHANGED examine superclass for power/apc
ADDED universal maxcharge readout for all the powercell types.
CHANGED using examine superclass on machinery/light, removed redundant description code

FIXED weapon/virusdish use a description field.
TWEAK lowercased some of the portable generators.

Fixed improperness of pacman names