CMS-1028 Content Manager Edit Form - Fix array handling for FormItemSets

Added FormItemContainer, FomrItemSetContainer, InputContainer. FormIteContainer is generalization, InputContainer and FormItemSetContainer is specific container for Inputs and FormItemSets accordingly.

Fixed occurrences issues.

Collapse/Expand button is functioning now, FormItemSet component refactoring and UI fixes
CMS-1028 Content Manager Edit Form - Fix array handling for FormItemSets

Fix unable to remove item (input or FormItemSet) from persisted items.
Merge branch 'master' of github.com:enonic/wem-ce into CMS-1028

Conflicts:
	modules/wem-webapp/src/main/webapp/admin/resources/app/view/contentManager/wizard/ContentWizardPanel.js
CMS-1028 Content Manager Edit Form - Fix array handling for FormItemSets

Fix resetting Display name during editing
Merge pull request #128 from enonic/CMS-1028

CMS-1028 Content Manager Edit Form - Fix array handling for FormItemSets