Image background

[nam-van-nguyen]

Would you please review and merge the code that supports the following?

1. Themes with or without background images
2. Users can put additional .ini files in the config folder for additional theme
3. Users can edit colors of each theme to match their preference, with Reset button to restore to default values
4. Moved center UI area code from Widget to OpenGLWidget
5. Possibly improving some smoothness issues with scheduling changes and the upgrade to OpenGl widget

[nam-van-nguyen]

FYI, I just added a new branch, https://github.com/nam-van-nguyen/PianoBooster/tree/keyboardcommands

Added support for using the Piano keyboard keys as command (88 keys):

• Added preference keys startStopKeys (default "21,108"), rewindKeys (default "21,107"), speedUpKeys (default "21,105") and speedDownKeys (default "21,103")
• These are comma separated list of integer Midi notes, when pressed in a same time, the application would start/stop, re-wind, speed up /speed down
• For speed up/speed down, when press first time, it starts increase/decrease every half a second, press again to stop the speed change

The above keys combination can be changed in the config. .ini file as desired or depending on keyboard size.