#4675: Improving MapStore Performances

[allyoucanmap]

Description

This PR introduces small improvements to the mapType HOC of BaseMap to import dynamically the map libraries. This work does not include all the needed fixes to align the Map plugin and BaseMap components in a single one but it should be integrated in the work started by @mbarto in this branch https://github.com/mbarto/MapStore2/tree/basemap_review.

Improvements:

• dynamic load of map libraries inside BaseMap component (geostories, widgets, ...)
• allow children as tools inside BaseMap component

The dynamic loading will split the map libraries from the main bundle and it should help to increase a bit the performance, in particular for custom project

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

Issue

What is the current behavior?

#4675 small improvement for MS bundle

What is the new behavior?

see description

Breaking change

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

• No

Other useful information

[coveralls]

Coverage increased (+0.02%) to 80.889% when pulling aa76e17 on allyoucanmap:base-map-dynamic-import into ac91678 on geosolutions-it:master.