Improve spec for DocumentController

I remove the dependency from DocumentController to DocumentService which
appeared in mocks for DocumentService methods.  These mocks were quite a
copy of the DocumentService methods which is not desirable.

Instead, now I use a RAM file system and only mock the getRootPath
method of DocumentService which now returns "ram:///".
Revise embedded document list

I revise the code to display an embedded document list after changing
the document list code.  I also add the missing test specifications.