Support Custom Gauges in HUD Config UI

[MjnMixael]

This PR adds 90% of the support needed for Custom Gauges in HUD Config. Custom gauges can now be individually colored to the user's preference. This also adds a new .hdp file to save the player's HUD color preferences. I felt this was a better way forward than trying to add it directly in the player file and having to bump the player file version causing a cascade of changes needed. The new file will be used if present, otherwise it will use the data from the player file.

Also added here is framework for custom gauge Visibility and Popup toggles but those are currently unimplemented and will need further table flags, testing, and for Popup, some kind of way to trigger when they should popup. Might really only be useful for Scripted gauges? I haven't planned that all out yet. That will be a future PR.

The display color of a custom gauge matches built-in gauges with one exception**:

1. SEXP defined color
2. User defined color
3. Color based on gauge type ** New. This is how custom gauges currently get their default color.
4. Default main preset color