Frontend quantities

(requires follow-up Ic89b54e39b3fd759bad568fc412e192b237da320 to work properly)

Change-Id: Iaaa1e0ac05f025be85a95d9a99d60329e89a98db
QuantityType UI implementation

First iteration of the JavaScript user interface for the Quantity data type.
(requires change I4d4252fcb8d14bf9324e7ec9c63d406592c0637a to work correctly)

Change-Id: Ic89b54e39b3fd759bad568fc412e192b237da320
Merge "Frontend quantities"
Merge "QuantityType UI implementation"