Spider tweaks

Reworks the spider "fur" to something marginally more realistic, links the chitin and fur branches, and adjusts a dream now that spiders sleep in webs.

Fixes #10616.
Incorporates BevapDin's fix and corrects a few debuffs I missed.
Gives Insect the compound-eyes mutation too.
Removes compound eyes from spiders.

Apparently this one was mis-located since Whales-era.  Better late than never.
Adds survivor machete to Eskrima weapons.

The other machetes are already in there.
Make cameras easier to find and harder to make
Add sanity-checked methods to item selections.

When fetching an item from the map (or from a vehicle) by using an index
into the list of items in that tile, we should verify the index is still
valid.

Prevents a couple of crashes relating to subscripting a non-existent
index past the end of a list.
Merge pull request #10623 from KA101/muts

Spider tweaks
Merge pull request #10658 from Rivet-the-Zombie/machetefix

Adds survivor machete to Eskrima weapons.
Merge branch 'easier-cameras' of https://github.com/Coolthulhu/Cataclysm-DDA into merge2
Merge branch 'merge2'