Add spindle state icon

- add icon showing spindle state
- add tooltips for the state icons
- hunting for the slow sending of commands (esp. when jogging), added
and tweaked some diagnostic output
- refactored the grbl state parser and simplified the incorrect
measurements logic
- cosmetic formatting fixes
- added coolant icon
Experiment with sleep times in waitForOk

Reduced some sleep times, seems to help jog performance.
Fix a swathe of compiler warnings

Fixes a mixture of mostly harmless warnings in the QextSerialPort and
log4qt libraries.
Minor fixes that clang warns about

Clang complains about different things to gcc; MacOS defaults to
clang.
Trim strings in waitForOk

Trim some diagnostic strings to prevent stray \r's in the log
Poll grbl state during send file

Poll the grbl state when sending a file. We might want to make this less
aggressive later.