uimenu_entry: add optional 'extratxt' variable for secondary text (such as symbol placement)
int entry.left: offset from left edge of main entry text
nc_color entry.color: color of text
std::string txt: the text itself.

For example, see 'editmap' class
Map editor: Move into editmap class, fixed fields, added furniture, added line/rectangle/circle drawing of terrain/fields/traps/etc.

Completely functional, however some UI details may change, in particular switching between shape resizing / movement and tile selection
editmap: fix reversed "J" and "K" movement keys
editmap: adjust help strings
editmap: fix field density hilight offset
Merge remote branch 'origin/master' into map_editor-refactor
Reworked input and help systems to make more sense, various cosmetic fixes
"All seeing eye" draw mode optional
Merge PR #2479 - Map editor improvements