This means we have to maintain this file. However we want packagers
to be able to reproduce builds from tags etc, so we need to provide
the lock file I think.
This links the python bindings statically to libdeltachat.a if the
DCC_RS_DEV environment variable is set to the project's root. This is
a little simpler then requiring the manual CFLAGS and LD_LIBRARY_PATH
tweaking.
It also adds a script to easily invoke the integration tests locally
without forgetting steps.
