[Submission] Date & dropdown not properly indicated as mandatory

[KevinVdV]

Describe the bug
When you have mandatory oneboxes or textareas & you add some metadata, the mandatory fields will receive a red border & the mandatory text pops up. This doesn't work for the date / dropdown fields if they are mandatory.

To Reproduce
Steps to reproduce the behavior:

1. Alter the submission-forms.xml to make a date and a dropdown field mandatory.
2. Restart the REST tomcat
3. Start a submission & add some metadata to the title
4. The Abstract field will receive the red border & a help text to indicate that this is mandatory will pop up.
5. The above doesn't happen for the date / dropdown fields.

Expected behavior
The red border should show up & the required text should be displayed.

[artlowel]

Fixing this will take an estimated 2h

[artlowel]

Atmire is interested in claiming this

[artlowel]

After further analysis it turns out these fields can already be styled as invalid correctly, but they're not because a 'touched' mechanism already exists in the ng-dynamic-forms lib, and these specific fields only show errors when they've been touched first. However it doesn't work in practice: if you touch them without saving they don't become invalid, and if you save the touched status is reset to false.

I'd suggest this be fixed in the context of #835