qucs-doc: fix warning: '%'-style pattern rules are a GNU make extension
qucs-doc: update README
qucs-doc: add install

* add make install
  install all the generated PDFs
* overide all-recursive, build PDFs by default
* add ps2pdf dependency to convert technical.ps
add tutorial textmode

* thanks to Clemens Novak
* set workbook authors in alphabetical order
add tutorial RFResModels

* thanks to Mike Brinson