Fix timestamps displaying wrong date in UI.

Looks like the lower case d indicates day of the week. Need a capital D
to indicate the date.
Fix timestamps defaulting to local timezone.

The defaults for 'created' and 'modified' defaults and updates to
current timestamp, which is the time in the local timezone. This
conflicts with our assumption that all stored time in the database is
UTC and makes the UI display wrong times when the defaults are used.

Fix is to use utc_timestamp instead of current_timestamp. Note that this
fix is only valid if data is inserted through SQLAlchemy. Raw queries to
the database will still suffer from using current_timestamp as the
default.  This might be because MySQL's utc_timestamp function is too
new for SQLAlchemy to use yet?