cmake: Added custom NSIS templates

* Unused "gnuradio Desktop icon" option removed
* GNU Radio Companion can now be accessed from the Start Menu
search install prefix for qwt correctly
libqwt.so should take precedence over libqwt-qt4.so (qwt6 vs qwt5)
workaround for broken QIcon.fromTheme missing function
remove scipy references from gr-perf-monitorx
runtime: gr-perf-monitorx, make very sure we are using the right matplotlib backend before causing any problems by defaulting to a different one
docs: Include generated header files when generating doxygen documentation.
sphinx: Added sphinx source for gr-analog.
sphinx: Added sphinx source for gr-channels, gr-comedi, gr-fcd, gr-fec.
sphinx: Added sphinx source for gr-filter.
sphinx: Added gr-shd to sphinx docs.
doxyxml: Parse contents of namespaces (necessary for parsing pmt's doxygen).
sphinx: Add start of pmt sphinx docs.  Tidied gr sphinx docs.
blocks: fix file meta data source to handle repeat of files.
runtime: converting runtime core to gr namespace, gnuradio include dir.
runtime: fix include location
analog: update include dir to gnuradio/analog
audio: moved include dir to gnuradio/audio
channels: moved include dir to gnuradio/channels
comedi: moved include dir to gnuradio/comedi