Validate form after adding a new type

[wbazant]

Closes #553.

Formik can re-validate a field after setFieldValue, but doesn't do that for the whole form, and we have just a global validator (validateLocationStep). Trigger it after adding a new type so the form realises the types field is no longer empty.

[ezwelty]

@wbazant Thanks! This fixes the issue of Types still being red after adding a new type, but Types is still red when opening a blank form, which feels unexpected ("how did I already do something wrong, I only just opened the form!"). I'd expect a behavior more like the problem report, where the required field Problem type only goes red once another input is touched. Is that possible with Types?

[wbazant]

Thanks! I agree the type shouldn't be red on start, you've pointed it out in the original comment but I missed it. Bizarrely, it was configured to do it, and we have a bunch of them (some of which don't do anything). I'll review the other ones too, see #571