Replace Nls root property by layer root.

Nls root can be obtained from facet. Each facet represents one webtop layer.
Also remove unnecessary test(NlsHierarchy).
#WT-12 work 3h
Return 'parent layer' option

Parent layers now persisted, even if parent facet or module is renamed.
Switched from JDOMExternalizable to PresistedStateComponent for storing facet configuration.
#WT-12 work 5h
Add to WebtoperFacet NLS root API methods

Also rename Utils to WebtoperUtil
and remove getNlsRoots(Module) - now it is unnecessary
since we should obtain facet for PsiElement or VirtualFile.
Add WebtoperUtil.findFacetForElement for this purpose.
Refactoring: NLS name now obtained thought facet-owner
Add todo's
Fix bug with facet renaming
Merge branch 'feature/wt12redesing' into develop
Update wiki about plugin configuration

#WT-12 fixed work 3h