Simplified widget creation, added textboxE

Rewrote midiOut widget to use uisfSinkE (this is cleaner in some ways,
but a better improvement will come soon)
Simplified and commented mkWidget.  Added mkBasicWidget for simple
non-interactive graphic components.
Improved textbox, making it more responsive.  Added textboxE, an
event-based input version.
Merge branch 'development' of https://github.com/dwincort/Euterpea into development