Prevent quest items from being stashed, instead of items with no price

This lets us stash Scathelocke's Spellbook, which isn't a quest item and
has no price.
Allow multiple "req" lines per item
Change syntax for item requirements

Instead of "req=p,2", we now use "requires_stat=physical,2". Other stats
include: "mental", "offense", and "defense".
Merge pull request #1243 from dorkster/item_req

Item requirement improvements
ItemManager: Add missing error(...) on parsing failure
Formatting as defined in our astyle.sh rules
.mailmap: switch to Stefan Beller's personal address

Normalize to my personal address. I can still receive email at
the @googlemail.com address, but I tend to use @gmail.com nowadays.

Also add my new corp account.
Note that despite the private address being first,
Google owns the copyright as long as I am employed there.

Signed-off-by: Stefan Beller <sbeller@google.com>
Don't overwrite the character class with a generated title
Support unique power trees for classes
Don't display duplicate class titles
Add "requires_class" property to items
Better engine/classes.txt parsing

Also, don't translate "Adventurer", since class names are stored
untranslated.
Merge pull request #1237 from dorkster/fixes

Prevent quest items from being stashed, instead of items with no price
Merge pull request #1244 from stefanbeller/master

Small fixup in parsing ItemManager
Convert string to C-string for logging

Fixes #1245
Merge pull request #1246 from dorkster/fixes

Convert string to C-string for logging
Merge pull request #1241 from dorkster/power_tree

Unique power trees and item requirements for classes
replace 4 values with 1 vector
Merge branch 'master' into openGL