ColorPicker: new prototype for ColorButton() .Added _NoTooltip, _NoLabel flags. Changing _Alpha flag to _NoAlpha makes so much much sense and allow to revert default parameters to zero. ColorEdit4/Picker4 don't attempt to read/write fourth component, making ColorEdit3/Picker3 shorter/faster. Tooltip and Picker called from ColorEdit can have a title. Picker shows colored square. Moved ColorTooltip() to imgui_internal.h (#346)