Fix issue 417: Copying from result display doesn't work

Allow copy from editor or result window depending on which was selected last.
Enhancement 418: User option to automatically copy result to clipboard.

The result is copied automatically to the clipboard without any hot-keys if the
user selects the option "Settings > Behavior > Automatic Result to Clipboard".
Add Artem Golovinsky to credits.
Add a .gitignore file.
Implement #420: Radio Frequency (RF) book pages.

Thanks to James Yuzwalk.
Credit James Yuzwalk (book pages).
Removed unmaintained and unfinished parser.
Moved binreloc right under thirdparty.
Book: add missing <sub> around variable.
Book: change font size for variables and descriptions.
Book: normalize style.
Book: new RF SWR page, merge with previous Return Loss.
Book: Misc->Algebra, new log base conversion page.
Book: new Unit Conversions section, Temperature page.
Book: 2D/3D Objects sections -> Geometry.
Rename index file for the book.
Book: clean up quadratic equation page.
Book: clean up circle page.
Math Book -> Formula Book
books -> book