qucs-help: add documentation for subcircuit usage
transcalc: add widget windows icon
transcalc: add icon as resource
mac: icon is handled by .plist file on the

* platform dependent handling of the QApplication icon
allow BJT Vtf parameter to be negative

* Originally `Vtf` was a _POS_RANGE parameter,
  now it is a _NO_RANGE  (pos or neg)
* Recent models may use negative `Vtf` to fit the device to the model.
* With this changes we turn a simulator failure into a warning.
* See bug https://sourceforge.net/p/qucs/bugs/163/
cmake: for qucs-rescodes
fix lupdate warning
update translation files