ENYO-1836: improve library integration into designer's palette 

Related JIRA: https://enyojs.atlassian.net/browse/ENYO-1836, https://enyojs.atlassian.net/browse/ENYO-3394, https://enyojs.atlassian.net/browse/ENYO-3494

ENYO-3394: fix categories indicator state when a category is empty after a filtering
ENYO-1836: ignore a specific category of components in the palette, lighten palette item management (sort, comparaison, description)
ENYO-3494: fix a bad initialisation in Serializer

[DO NOT MERGE] Must be reviewed (first) by @yves-del-medico and is related to other PRs:
* https://github.com/enyojs/enyo/pull/523
* https://github.com/enyojs/layout/pull/61
* https://github.com/enyojs/onyx/pull/183

Enyo-DCO-1.1-Signed-off-by: Vincent HERILIER vincent.herilier@hp.com