Allow facts in datadir

[tuxmea]

An installation can use a fact inside the datadir setting.

datadir: "%{facts.node_data.hieradata_path}"

HDM should be able to also show data from a data dir which is set based on facts

[oneiros]

Looks like a duplicate of #157. Does this not work as expected?

[tuxmea]

Just tested. Works as expected.