[backends/vala] Split diagnostics in separate file
[backends/vala] Move options into application
[backends/vala] Fix makefile integration for vala
[backends/vala] Simplified namespaces
[backends/vala] Refactor dbus service
[backends/vala] Use external helper to parse

libvala has memory leaks which cannot be prevented at the
moment. Therefore, move the actual parsing out of process.