Show weapon range in the unit help browser.
Better default selected item handling in the unit palette.

Choice the first group instead of a hardcoded one for startup.
Choice the first item instead of a hardcoded one for startup.
Skip empty groups.
Don't show do_not_list unit_types.
Show multihex range of weapons in the help browser.
Support for overwritting hp_bar_scalling and xp_bar_scalling.
Store and getter for the do_not_list attribute.

The do_not_list attribute is an old one but was only used by external
tools. It suits for keeping out unit_types from the editor unit_type
palette.
Save extra map configs with the no_leader=yes attribute.
Use color shifted icon for palette groups if no active icon available.
Do not list "do_not_list" units in the debug create dialog.
Support for overwritting hp_bar_scaling and xp_bar_scaling.
NO_TERRAIN preprocessor symbol to allow campaigns not loading core stuff
Added a const qualifier.
Removed hardcoded terrain topics.
Enable terrain description context menu entry.
Cleanups which prepare for autogenerated terrain help sections.

Virtual parent terrain for every base one.
Added descriptions for the help browser's topics.
Introduced hide_help attribute.
Removed mixed forest terrains.
Copied terrain symbols to a more accesible place.
Changed the strings of base terrains to fit the *t convention.
Autogenerated terrain help sections.