Using QFileDialog directly on OS X can hang intermittently due to Qt
bug.

- Logging now always on to temp file
- User prompted to save temp file after disconnect
- Orphaned temp logs checked for on boot
- Logs saved to new save file location
- Log file starts/stops with first and last connnection

Also renamed from QGCSettingsWidget to SettingsDialog to better reflect
usage.

This avoids collision with main app SettingsDialog class

Map widget: make all connections that might suffer from multiple connect logic issues unique, found by Nyaruko

This way OS X correctly positioned menu items

This allows you to filter the list of parameters the widget displays.

This allows you to determine if full parameter list is ready if you
missed the parameterListUpToDate signal.

Also fixed bug in loadStyle

The dark css is the master and contains all style information. The
light css is the slave and only contains color information.

This allows you to filter the list of parameters the widget displays.

This allows you to determine if full parameter list is ready if you
missed the parameterListUpToDate signal.

Handy for testing without a real board

QSerialPort buffering too slow on Windows.

Settings versioning is handled at the uppermost level with a version
stamp.