Merge pull request #82 from blackwarthog/single-window

Single window
Update renderer_canvas.cpp

Remove unused Gdk::GC
Update renderer_bonestup.cpp

Use Cairo context to show text
Update widget_timeslider.cpp

Use Cairo to render the widget
Update widget_timeslider.cpp (2/2)

Use Cairo to render the timepoints
Update widget_keyframe_list.cpp

Draw background using Cairo
Update widget_gradient.cpp (1/2)

Render gradient to window using Cairo
Update widget_gradient.cpp (2/2)

Get ride of not used Gdk::GC
Update widgets_defaults.cpp

Draw brush size using Cairo.
Remove unused code.
Put code of render gradient to window to other function using a Cairo Context.
Do not gamma filter the colors for the moment.
Get gamma_filter outside Target_Cairo class and move it to synfig namespace
Build script
Configure script
Fix some includes

Conflicts:
	synfig-studio/src/gui/widgets/widget_gradient.h
Convert cellrenderer_timetrack to cairo