Improvements to Null values handling

[dferrand]

Multiple changes to null value handling:

• In addition to being in italic, a null value now has a highlighted background (as suggested by @mipjones)
• When a field is updated from a null to a non null value, the italic and highlighted background is now removed (fixes UX: update mode output formatting does not refresh when _null_ value is changed #403)
• Setting a field to null is now done by pressing shift+enter instead of entering null (or - for a field shorter than 4 characters). A tooltip indicates this information if the field is nullable. This allows setting a field to the "null"string (or "-" if shorter than 4 characters). (fixes UX: No obvious way to enter null value when in update mode #402)

[worksofliam]

The functionality is excellent! I love the Shift+Enter notice. Here are a couple of things I noticed:

Looks like some css issues with the columns:

When applying null, the font is not set to monospace as the other columns are, though it's not consistant:

[dferrand]

I made a few more changes:

• Fixed the css issues
• fixed the font
• column widths on result set are now adjustable. If you double click on the width adjustement handle, it will auto adjust the width to the content
• You can now choose to display both column name and label in the header

[sebjulliand]

Note: I just met @dferrand who asked for the status of the PR. This is a bump to not forget it 😅

[sebjulliand]

@dferrand can you resolve that small remaining conflict? Then I'll give it a go. Thanks!

[sebjulliand]

It's a great change, thanks @dferrand .
There are two little quirks though:

• Label and Name are inverted (see my comment)
• When displaying the joblog, cell content is not centered in the middle as it did before. Can this be fixed?

Before:

After:

Fixed these two points and resolve the remaining conflict and we'll be good to go !

[sebjulliand]

name and label are inverted here/

Suggested change

	case 'Name':
	cell.innerText = column.label;
	break;
	case 'Both':
	cell.innerHTML = escapeHTML(column.name)+'<br>'+escapeHTML(column.label);
	break;
	default:
	cell.innerText = column.name;
	case 'Name':
	cell.innerText = column.name;
	break;
	case 'Both':
	cell.innerHTML = escapeHTML(column.name)+'<br>'+escapeHTML(column.label);
	break;
	default:
	cell.innerText = column.label;