cmake version

Switched to cmake as a build system which was long overdue.

Small usability changes

The +/- in the timebase was pretty misleading. It's now "faster" and "slower". Plus re-compiled for the new IIR library to prevent missing symbols.

Bugfix release / filter upgrade

This fixes a bug where the save dialogue didn't have a field for the filename.
Using the latest version of the iir1 library with safer initialisation and new IIRNotch filter.

QT5 version

Moved over comedirecord from QT4 to QT5. This required only a few changes.
The program has now been tested extensively under Ubuntu Xenial.