Add professions at character creation

Make it possible to define various professions for the player to take at character creation. Each profession can add or subtract points from the player's available pool, and defines a set of items that the character will start with. In the future, professions may be expanded upon.

The default profession, currently dubbed "Unemployed", is the same as existing behavior, and costs 0 points.

There are also 3 sample professions in this commit (Wannabe Mechanic, Lab Technician, and Nudist), although the point costs may be unbalanced. You guys can modify them all you want, they're mostly for testing purposes (but are still not unreasonable for inclusion, IMO).

This does break save files and templates. However, adding or modifying professions will not break anything, and changing or removing profession identifiers will warn the player, and then assign a default profession to anything that relied on the old identifiers. Basically, I don't want to introduce another failure point for save files.