CMS-1743 Add type definitions for relationshipType_delete in RemoteService.ts

 Add strict typing for the parameter and result values of RemoteServiceInterface.relationshipType_delete()

 * Check the RpcHandler method in Java to find the exact values accepted and returned.
 * Use optional types (optParam?: string) where appropriate.
 * Avoid use of any as much as possible and use concrete types.
 * Look at types of space_list() and space_get() for reference.
Merge branch 'master' of github.com:enonic/wem-ce into CMS-1743

Conflicts:
	modules/wem-webapp/src/main/webapp/admin2/api/js/lib/RemoteService.ts
Merge pull request #267 from enonic/CMS-1743

CMS-1743 Add type definitions for relationshipType_delete in RemoteServi...