Improved dashboard component extensibility.

[jobosk]

Modified dashboard component in order to allow tags to be passed as a parameter even if there is no entity context.
In response to: #59

[jobosk]

Hi @K-Phoen , I updated this PR with your latest modifications regarding queries by tag to grafana.
I would appreciate if you could have a look and consider aproving.
In my team this change is really useful in order to use your component within techdocs, where there is no entity context available (but we can still get the entity tags).