ome-xml: Add joda-time 2.2 as a build dependency
ome-xml: Timestamp uses Joda Instant and DateTime internally for ISO-8601 dates

Internal timezone representation: UTC in milliseconds (Instant)
Input timezone representation: Defined in ISO-8601 string
Output timezone representation: UTC

The date handling is made reproducible and consistent by using UTC
everywhere.  If it's a non-UTC date on input, we convert to UTC.

The input and output of native Java Date and Calendar types is not
currently affected; we don't convert to UTC in input, but this is
an amendment which should be considered.
ome-xml: Timestamp: Remove unneeded imports
ant/toplevel.properties: Add joda-time-2.2.jar
ome-xml: Timestamp: Remove pointless DateTime usage in asSqlDate()
scan-deps.pl: Add joda-time
ome-xml: Timestamp: asDateTime requires timezone
ome-xml: Timestamp does not call super(null)
build: Add additional joda-time dependencies
ome-xml: Timestamp logs parse errors at debug level
Merge pull request #619 from rleigh-dundee/timestamp-precision

ome-xml: Improve Timestamp date handling and precision