Remove old php build scripts

They are still in the repo, but they are just no longer needed
And all the rest...
Remove auto generated files

This is just a mess to maintain. If people can't be bothered
to install the autotools they will just not be able
to compile this...
Moved the automake scripts into a separate dir
First version of a port to gtk3

Largely untested. In particular the toolbar customization
does not yet work
Merge branch 'gtk3' of github.com:x2b/xournalpp into gtk3
Merge branch 'gtk3' of github.com:x2b/xournalpp into gtk3
Merge branch 'gtk3' of github.com:x2b/xournalpp into gtk3
Merge branch 'gtk3' of github.com:x2b/xournalpp into gtk3