Transaction log in admin UI

Summary:
Created TransactionLog widget, which is now used in User and Admin apps.
The transaction log table for admins displays additonal User column.

Test Plan: ./phpunit

Reviewers: #hkccp_developers, vanmeeuwen

Reviewed By: #hkccp_developers, vanmeeuwen

Subscribers: bohlender, #hkccp_developers

Differential Revision: https://git.kolab.org/D1360