Add "dots" freehand algorithm (change to ButtonSet the selection of FreehandAlgorithm)
Add ResourcesListBox as a generic version of PalettesListBox
Remove references to allegro_message() from outside of she library
Use she::error_message() in app_main()
Win: Use MessageBoxW instead of allegro_message() in she::error_message()
Add she::Font class (wrapper of Allegro FONT)

This is an huge refactor to avoid handling Allegro FONT directly. Some
changes:
* Add she::System::defaultDisplay/Font, createRgbaSurface, loadSurface,
  and loadRgbaSurface.
* Rename she::CreateSystem/Instance to she::create_system/instance.
* Remove ui/font.cpp and move ui/fontbmp.cpp to she library.
* ui::IButtonIcon uses she::Surface instead of BITMAP.
* Rename she::LockedSurface::drawAlphaSurface -> drawRgbaSurface
* Rename ui::SetDisplay -> set_display
* Rename _ji_font_text_len -> ui::Graphics::measureUIStringLength
Change ui::ImageView to use she::Surface instead of Allegro BITMAP
Remove <allegro.h> from resource_finder.cpp
Separate Options dialog in different sections

* Add ui::Panel widget
Add "Zoom with Scroll Wheel" option (on/true by default)
Now ui::Graphics uses she::Surface instead of Allegro BITMAP
Fix regression bug in SkinTheme::sliceSheet() introduced in dbad153698a552656dde17be2d9a9a203fdc1452

The skin's sprite sheet is loaded as an RGBA surface, and slices must be
created as RGBA sub-surfaces.
Add "slice" ink and tool (it is not yet implemented)
Use ui::Graphics instead of Allegro in Editor's brush preview routines

* Remove color_utils::color_for_allegro()
* Rename editor_draw/move/clear_cursor() -> draw/move/clearBrushPreview()
* Rename Editor::get_raw_cursor_color() and Editor::is_cursor_mask()
* Add Graphics::get/putPixel() and Graphics::width/height()
* Add SetClip class
Rename _unittest.cpp files to _tests.cpp
Fix tests/test.h
Remove ui::Widget::isScancodeMnemonic() member function
Remove some references to <allegro.h>
Merge she::Color and ui::Color types in gfx::Color
Add button to create new folders in FileSelector (issue 233)