fix Sectopod weapon fire and hit sounds

They're supposed to be lasers as opposed to silence on fire and a zombie bite
on hit, I think...
fix for visible unit button
fix ICONS.PCK are res free
Adding cancel button on New Game State to go back to main menu.
Fix for https://github.com/SupSuper/OpenXcom/issues/240 , misleading
error message.
refactor AggroState
fix from hmaon
pathfinding refactor

missiles finding a path shouldn't check for blockage by a target.
add a boolean argument to toggle this behaviour
fix for bad blaster behaviour

thought this was a bug in pathfinding or the waypoint allocation, turns out
it was a just a bug in blaster launchers in general :D
fix for research completed palette

multiple 16-color updates in a row; actually not sure how any of the 16-color
update cases were working
fine tuning for blasters

this should stop it pathfinding through targets that AREN'T our target,
as well as closed doors, or anything else that blocks the LOS of the
path of the waypoints, including the final waypoint.

if the final viable waypoint isn't the same position as where the target
is standing
Translation: Changed some translation keys.

We shouldn't use underscore + number suffix in normal translation keys, now that
they get added automatically by the translation system. So I changed
STR_WEAPON_1 to STR_WEAPON_ONE and STR_WEAPON_2 to STR_WEAPON_TWO.
Translation: More complete sentences.

- STR_EQUIPMENT_FOR_craftname
- STR_SELECT_SQUAD_FOR_craftname
Translation: Better support for number-forms.

- STR_n_UNITS_IN_EXIT_AREA
- STR_n_UNITS_OUTSIDE_EXIT_AREA
Translation: Proper question when abandoning game.

Only Spanish really needed this, but it's proper translation code.
- STR_ABANDON_GAME_QUESTION
Explosive Efficacy Rules

making them shoot is one thing, making them not shoot is another.
ditch faulty paths.
merge fixes from hmaon
some changes to efficacy
make ResearchState preserve Geoscape palette

NewResearchStateAvailable can push ResearchState which resets all 256 colors
If it's followed by further notifications, they are displayed in an incorrect
palette. This change makes ResarchState save its palette and restore it on OK
click; thus harmony is restored.