[FEATURE]: Allow (un)checking groups of axioms more intuitively for OWL 2 import

[mnamici]

Description

We should tweak the axiom selection dialog for OWL 2 import so that it allows to (un)select entire groups of axioms more intuitively for new users and also give a more descriptive overview of what is selected when parent items in the list are collapsed.

Motivation

The current axiom selection dialog behavior is a bit counterintuitive. In particular the Select All and Deselect All buttons only affects the axioms whose checkbox is visible, meaning the container item is not collapsed.
This is on purpose and motivated by the fact that blindly selecting all axioms at ones is an uncommon operation, and gives the user a way to select only specific subsets of axioms in an easier way without having to click each of them individually.

The problem however is that this sometimes can also look like unintended behavior, for example if you don't expand any list and click Select All nothing actually gets selected, so a first time user would probably think that the button does not work as intended.

What I suggest to solve this issue is to add checkboxes also to parent items in the list, and have it behave in such a way that the checking/unchecking of the parent checkbox will check/uncheck all the item children recursively, then let the Select All/Deselect All buttons actually operate on the entire set of axioms (as their label suggests).

Example Use Cases

For reference here is for example how a similar component looks in Eclipse on the Install new software dialog: