Make widgetset and theme compiled on maven project import in Eclipse

[vaadin-bot]

Originally by @mstahv

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Currently eclipse is instructed to execute widgetset update, but not compilation on project import (onconfigurationchange), which doesn't really help users at all. Same for the theme. Also the compilation should be done or the obsolete goals should be removed.

See this discussion for more details:
https://dev.vaadin.com/review/#/c/12984/

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Imported from https://dev.vaadin.com/ issue #19556

[vaadin-bot]

Originally by @hesara

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Addressing this in the branch feature/appwidgetset where the obstacles for doing this have been largely addressed.

[vaadin-bot]

Originally by @hesara

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Under review at https://dev.vaadin.com/review/#/c/13269/

[vaadin-bot]

Originally by @hesara

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Fixed in the feature branch

[vaadin-bot]

Originally by @hesara

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Reverted in https://dev.vaadin.com/review/#/c/13271/ because this caused more problems than it solved (refresh not working correctly; workspace artifact resolution not in use which leads to actual errors in the project).

[vaadin-bot]

Originally by lrozenblyum

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Another idea added here: https://dev.vaadin.com/ticket/19725#ticket