Show persistent message when DataHarmonizer can't be shown because template hasn't been selected

[pkalita-lbl]

In the situation where a user visits the Data Harmonizer screen (err, or, Sample Metadata screen -- see #1901) before selecting a template, they currently get a modal dialog that says "No tabs will be present until one or more templates are selected in the Sample Environment form". Once the modal is dismissed, the user is left with a partially-initialized HarmonizerView.

This task is to change the logic of HarmoinzerView so that if a template hasn't been chosen yet, a persistent message should be displayed (i.e. not a modal). And nothing else should be rendered (i.e. no help sidebar, no validation controls, etc).