First implementation of map widgets

[offtherailz]

Description

This provides a first implementation of map widgets (charts) functionality.
See the mockup for details

Issues

• connected to Support for widgets on map #2324

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)

• Feature

What is the current behavior? (You can also link to an open issue here)
No charts available

What is the new behavior?
You can add charts to the map as in the Mockup.

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

• No

Other information:

• The missing things to improve functionalities are listed in the related issue
• The query builder is now more usable for general purposes (not 2 way binded to the WFS query)
• Important Note: This pull request introduces and uses some HOCs that should be used everywere, to provide a more consistent interface and simplify/speed up development:
  • emptyState: shows an empty state view (like this) instead of the component, providing a test function. Tj
  • loadingState: shows a loading spinner instead of the component. By default gets the loading prop but supports also a test function.
  • propsStreamFactory: allow to provide a function as argument of a component that generates the properties of the component it is applied: useful to make reusable widgets that do complex async data flows.

[coveralls]

Coverage increased (+0.3%) to 81.006% when pulling 88fc23d on offtherailz:widgets into dff8fb5 on geosolutions-it:master.

[mbarto]

Some comments:

• Esporta dati --> Scarica immagine
• delete confirm dialog --> not translated (in italian at least)
• line and histo charts --> colors are not updated on combo selection
• missing title / help button in gauge dialog

[coveralls]

Coverage increased (+0.3%) to 81.007% when pulling 33547ac on offtherailz:widgets into ddeaa57 on geosolutions-it:master.

[coveralls]

Coverage increased (+0.3%) to 81.007% when pulling 87e1264 on offtherailz:widgets into ddeaa57 on geosolutions-it:master.

[coveralls]

Coverage increased (+0.4%) to 81.072% when pulling 756a4d9 on offtherailz:widgets into ddeaa57 on geosolutions-it:master.

[coveralls]

Coverage increased (+0.4%) to 81.06% when pulling 15868c2 on offtherailz:widgets into ddeaa57 on geosolutions-it:master.

[coveralls]

Coverage increased (+0.3%) to 80.977% when pulling a203383 on offtherailz:widgets into ddeaa57 on geosolutions-it:master.