Adds grappling hook.

Like a (slightly) lighter 30 foot rope but easier to get out of
sinkholes with this one. Crafted or found rarely in sporting
goods/hardware areas or (slightly) more commonly in
military/EMS/survival stuff.
Final fix.
Tweak.
Glyph tweak.
Grammar tweak.
Actual final fix.

For real this time!
Merge branch 'grappling-hook' of https://github.com/Rivet-the-Zombie/Cataclysm-DDA into Rivet-the-Zombie-grappling-hook
Reconciled with #6347

As stated in the PR discussion, this needed to have the
terrain-changeover implemented.  Doing so as part of merge.