Changed many functions in the abstract *Link classes to be const. This facilitates setting other functions as const. The metadata for specific links are reset when the links are added.

Minor cleanup, fixed a bug where the serial port would not connect on first application launch on Linux

qextserial library is no longer maintained, suggest we move
to this library, also greater chance for thread safety,
library now builds in cmake, will add Serial2 sources to
handle the new qserial, should easily plug into serial interface
now.

Added not yet working version of logging / log replay, fixed ALL bugs in main window, enabled full persistence in main window and serial link.

Added new options for windows serial port, fixed a number of bugs, added customizing options to instrument widgets