Provide ALIAS to wms getfeatureinfo(gml), wfs and vector datasources

[pelord]

Please check if the PR fulfills these requirements

• The commit message follows our guidelines:https://github.com/infra-geo-ouverte/igo2/blob/master/.github/CONTRIBUTING.md#git-commit-guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

What is the current behavior? (You can also link to an open issue here)
There is no way to provide alias to datasources.

What is the new behavior?

1. By using the sourceFields param (also used for ogc-filter) , you can provide an alias to a field

"sourceFields": [
{"name": "fieldname", "alias": "fieldAlias"},
....
...
]}

2. When you click on map to query the vector source, the result is now grouped with the layer title instead of a generic group name named "Clicked feature". e.g.
   Before:
   

After:

Does this PR introduce a breaking change? (check one with "x")

[ ] Yes
[x] No

If this PR contains a breaking change, please describe the impact and migration path for existing applications:

Other information: