modules: add libyaml module

Signed-off-by: Tomasz Grabiec <tgrabiec@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
cloud-init: depend on libyaml

Signed-off-by: Tomasz Grabiec <tgrabiec@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
httpserver: add missing libyaml.so when cloud-init module is not included

httpserver's DSO is linked against libyaml but does not include it in
its manifest. Fix by depending on libyaml module.

Makes the following dmesg line go away:

  could not load libyaml-cpp.so.0.5

Currently it doesn't cause any run-time problems because the
functionality which uses libyaml is run only when httpserver is
configured via cloud-init, in which case libyaml is already included.

Signed-off-by: Tomasz Grabiec <tgrabiec@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>