Addon birth options

Adds an options menu to the birther dialog.

This lets addons specify extra options on a player's birth. These are treated as normal options, so they are saved in the player's profile. However, the value of this option at the player's birth is stored on the player itself. This is to prevent needing to switch options if you switch between save files that are using different options.

Adds the ToME:extraBirthOptions hook, as well as a generic OptionTree dialog.

Example Addon: http://te4.org/games/addons/tome/grayswandir-test-birth-options