Fix linking of Trace2uml on Ubuntu Trusty

On Trusty (at least) libcairo isn't found automagically but has to be
explicitly specified to the linker.
Use 'pkg-config --libs gtk+-2.0' for this.
debian/control: Removed the dependencies upon wx2.8
regenerate_all.sh: Use 'git describe' to label current version
build_all.sh: 'make -j6' to speed up the build.
genmakeinst.sh: regenerate / make / install packages