Durr, even more overmap vs. river vs. bridge boundary checking

Dunno if bridges between overmaps should even be legal.
Initialize webs properly in mapgen. Avoids weird bug where fields stop updating if you burn the webs.
Add launcher for Linux/OS X users to double click
Fix NPC teaching
Remove redundant check for flamable clothing.
Add message for skill increases while reading
Add offset coordinate members to player class to support persistent view shifting.
Use new offset coordinates to adjust origin of normal draw() and look_around() operations.
Remove L as a default keybinding to free it up for view shifting.
Add new view shifting actions.
Add implementation for view shift commands.
Add default keybindings for cardinal view shifting commands.
tweaking silo roomgen

to avoid single room being walled off from the rest.
Initial rng '--seed' mechanism. From any string.

This only guarantees one sort of consistency: with the same input,
on the same system, and of course with the same character build,
on a new world, the state, including the overmap & starting location
should be identical.

good enough for benchmarking.
Return bandages and first aid to inventory when they are applied to a limb to no effect.
Add water to crafting materials if near water source
Added new flag for terrain water sources
Toned down velociraptor aggression even more
Added human flesh to meat trigger
Stop consumption of batteries if player internal battery is full
Bugfix for super toolkit recipe
Bugfix for powder meds not appearing in containers