Almost complete the VISCA protocol support...

But the code is messy and the code is not tested.
Need to refine the code.
Fix some bugs.

The VISCA is still not tested with the real camera.
Clear the serial every time before we query pos or focal info from it.
Now the VISCA conf data can be read and dump. But the code is ugly...
Fix some bugs.
Add some UI interfaces.
Add the velocity setting UI interface.
Config file update.
Merge branch 'feature-VISCA' into develop