admin: Improve logging

This commit does the following:

a) Removes all unnecessary logging calls.
b) Adds a logging mechanism for post-mortem analysis.

The new logging mechanism, accessible from admin.utils.admin_log, logs
by default logs the name of the user and the caller view and allows the
user to add useful info such as the arguments for this view.
Merge branch 'feature-admin-logs' into feature-admin