Port changes:
* Remove the overriding patch of boost::asio:
now EINPROGRESS is handled properly, before it was not.
* Remove the overriding patch of websocketpp:
added an equivalent patch into cadabra2 source,
it is easier this way. Before such function didn't
exist in the websocketpp interface.
* Add the patch for pull/82:
missing #include / removal of unnecessary prefix calculation.
* Change cmake -> cmake:outsource.
* Switch to python3 because it links to python3 anyway,
even though it claims to support python2.
* Add DOS2UNIX_FILES for cmake/version.cmake for one patched file.
* Remove post-patch: added a similar patch under files/
* Remove post-install: stripping is now done by the project.
* Remove post-install-GUI-on: icons are now installed by the project.
Testing:
* Runs fine, shows correct results for examples from the online manual.
