succesful build/debug

- corrected current line highlighting when there's empty string
- introduced theme presets like "ltblue_theme()" in stylesheeted to
simplify client code
- added rect::event_info class
- removed dirty "in" pointer in rect
- refactored textbox virtual event callbacks so their declarations are
more specific
- set_focus bug corrected - wasn't setting "in" to its group owner -
repaired by removing "in" pointer
- got rect::clip flag to working; introduced
get_clipping_parent/get_clipping_rect functions that look for the first
clipping parent in rect tree
- focusable, preserve_focus variables
- added blacklist in textbox
- added focused style in stylesheets
- introduced color constants in graphics::colors

available SDK:
tetris, texteditor
focus chaining

- added working gen_focus_links function and focus_prev, focus_right
properties
property guard

added property guard;
need to resolve strange bug when middlescroll is clicked in settings
succesful build & debug

- added is_valid_func to ui, unknown glyphs are replaced with space in
drafter::draw
- corrected draw_text pos/parent policy so both are absoltue now (thus
corrected bug with strange middlescroll behavior)
- corrected caret mapping
- focus handling is now done in rects rather than globally by gui::group
(handle_tab, handle_arrow routines)
- get_clipping_rect is now just returning rect_ltrb clipping_rect that's
calculated on the go in rect::update_rectangles
- introduced one-line property_textbox
succesful build & debug

- updated animatorandconfig demo
- introduced callbacks to config, but config itself needs rebuilding
with more modern pattern
- setters/getters in properties
- next optional rect routine: handle_enter
- finally corrected caret mapping
todo update