#2691: Sort table widget functionality

[offtherailz]

Description

Enable sorting for widgets.
Draft because:

• Missing unit tests
• More testing about possible corner cases

Please check if the PR fulfills these requirements

• The commit message follows our guidelines: https://github.com/geosolutions-it/MapStore2/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (check one with "x", remove the others)

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

Issue

What is the current behavior?

#2691

What is the new behavior?

Columns sorting enabled for widgets

Breaking change

Does this PR introduce a breaking change? (check one with "x", remove the other)

• Yes, and I documented them in migration notes
• No

Other useful information

[coveralls]

Coverage decreased (-0.008%) to 83.261% when pulling 7babb5f on offtherailz:sort_widget into b14f2bf on geosolutions-it:master.

[tdipisa]

@myrdstom since you have provided PR #6119 I think we can close this one, right?

[myrdstom]

Yes @tdipisa , it can be closed