GUI features request & misc

[LowPowerLab]

Would be great if the GUI would include some controls to turn features on/off, some of which are only available through the command line.

• timestamps to include/exclude the milliseconds (or do this by default when they are all just 0's ?)
• allow to change the visible window span (--buffer option)
• allow to change the COM/serial port in the GUI - and show CONNECTED / DISCONNECTED status - for instance if serial port connection is lost for whatever reason

Would be nice to remove any dependencies to python and just have a standalone executable.
Any chance the program could be compiled into an executable? I tried it with pyinstaller but I ran into all sorts of issues.

BUG: I noticed if the USB is disconnected the SPS starts decreasing instead of going to 0.

[MGX3D]

Check out version 1.0.4:

• timestamps now change to second or millisecond depending on the range in view. This now also works when you zoom in.
• SPS rate now calculated differently (red if <100, yellow if <500, white otherwise) and automatically sets to 0 when there is no data.
• UI also shows connectivity state:

• Pause/resume buttons now change state correctly.

The rest of the suggestions/asks will have to wait for the next rev of the UI, as matplotlib is not exactly friendly to drawing UI features like this.