Add dependency graph to cmake-server
Currently, CMake is able to generate a dependency graph using the
--graphviz command line option. Unfortunately, it is only possible to generate this graph in the dot format, making it necessary to parse the output before being able to programmatically interpret it.
It would be nice if this graph was available in a format that is easier to parse; JSON for example. cmake-server seems to be the logical place to implement this functionality since it also provides a lot of other interesting information about targets.