773: Auto download parameters on CONNECTED

Work in Progress.  TODO:

- [x] Check !is_flying before sending parameter-get request (Parameters.java:154)
- [x] Start progress bar in parameters automatically
- [ ] Window leaks when leaving parameters page.
- [x] Make sure only one parameters download can happen at one time
- [ ] fix parameters download auto-restarting
It should be FIRST_HEARTBEAT event. Because when there is a connection doesn't necessary means the drone is connected, just the pipe.