Update styling on in-line forms

[ScopeyNZ]

Couple of design notes for the new in-line edit forms:

• Fields should be using the "stacked" mode. Labels should appear above inputs. This can be done by adding the stacked class to the form-group container:

Old:

New:

• Responsive min-width should be updated. Specifically for TinyMCE that's looking a little cramped:

• In-line edit form has horizontal scroll:

• When in edit mode with a reduced window width the TinyMCE right border is lost:
  

Add it here if there was anything I missed (cc @clarkepaul - let me know if you want to run through this together in more detail).

[clarkepaul]

Apart from making the editor area bigger we'll need to create a separate issue to organise the TinyMCE options.

[brynwhyman]

At least the above two points appear to be inherited from core styling. See here for details silverstripe/silverstripe-admin#655

[brynwhyman]

I'm changing this to impact/medium.

[raissanorth]

It appears that the first point has already been actioned upon.

See wide screen size:

See narrow screen size:

[raissanorth]

There are some weird semi-states as well... 🤔

[clarkepaul]

If this hasn't been fixed, can we make sure there is an issue to capture it (or let me know to capture it), it should nicely for smaller sizes.

[NightJar]

Closed in #478

[brynwhyman]

If this hasn't been fixed, can we make sure there is an issue to capture it (or let me know to capture it), it should nicely for smaller sizes.

@clarkepaul this wasn't fixed by this PR. I've raised #483 to track it.

[NightJar]

It was a run-on effect of the scrollbar and styling issues addressed in #478 and #487 respectively