Hide metadata labels without value

Conflicts:
	package.json
	src/app/+search-page/search-filters/search-filters.component.ts
	src/app/core/auth/auth.effects.ts
	src/app/core/auth/auth.service.ts
	src/app/core/auth/server-auth.service.ts
	src/app/core/data/comcol-data.service.ts
	src/app/core/data/community-data.service.ts
	src/app/core/data/data.service.ts
	src/app/core/data/item-data.service.ts
	src/app/core/shared/dspace-object.model.ts
	src/app/header/header.component.spec.ts
	src/app/shared/auth-nav-menu/auth-nav-menu.component.ts
	src/app/shared/testing/auth-service-stub.ts
	yarn.lock

Initial German Translation 

Issue #295 Dutch translation

Czech translation

Fix for authentication

Update version of Bootstrap per CVE-2018-14041

Issues 252,253: Browse by title and browse by metadata (author)

Conflicts:
	src/app/core/shared/operators.ts

Resolvers for item, collection and community home page