Refactor struct trap

Made some members to private, added getters for them.

Added trigger function, common for monster and player
Added can_see function to check for visibility.
Add missing visibility check for traps in cata_tiles
trigger existing traps when placing a new one there.

If the character sees the existing trap, don't trigger just tell.
Merge remote-tracking branch 'BevapDin/traps-in-tiles' into FrankenMod