CMS-3754 Let TabMenuItem accept an Action to be executed when remove button is clicked
Merge remote-tracking branch 'origin/master' into CMS-3754

Conflicts:
	modules/wem-admin-ui/src/main/resources/web/admin/apps/content-manager/js/app/ContentAppPanel.ts
	modules/wem-admin-ui/src/main/resources/web/admin/apps/schema-manager/js/app/SchemaAppPanel.ts
	modules/wem-admin-ui/src/main/resources/web/admin/apps/schema-manager/js/app/view/SchemaItemViewPanel.ts
	modules/wem-admin-ui/src/main/resources/web/admin/apps/schema-manager/js/app/wizard/ContentTypeWizardPanel.ts
	modules/wem-admin-ui/src/main/resources/web/admin/apps/schema-manager/js/app/wizard/MixinWizardPanel.ts
	modules/wem-admin-ui/src/main/resources/web/admin/apps/schema-manager/js/app/wizard/RelationshipTypeWizardPanel.ts
Merge pull request #920 from enonic/CMS-3754

CMS-3754 Let TabMenuItem accept an Action to be executed when remove but...