Add amoc header info to bulletin data

[adamhsparks]

BOM serves useful information about validity times and issue times and dates for the bulletins. This would be good to include in a printed metadata header as the historical and current weather station data have printed about them.

Example amoc:

    <amoc>
        <source>
            <sender>Australian Government Bureau of Meteorology</sender>
            <region>Western Australia</region>
            <office>WARO</office>
            <copyright>http://www.bom.gov.au/other/copyright.shtml</copyright>
            <disclaimer>http://www.bom.gov.au/other/disclaimer.shtml</disclaimer>
        </source>
        <identifier>IDW14199</identifier>
        <issue-time-utc>2019-03-21T20:30:00Z</issue-time-utc>
        <issue-time-local tz="WST">2019-03-22T04:30:00+08:00</issue-time-local>
        <sent-time>2019-03-21T20:30:55Z</sent-time>
        <expiry-time>2019-03-22T20:30:00Z</expiry-time>
        <validity-bgn-time-local tz="WST">2019-03-22T05:00:00+08:00</validity-bgn-time-local>
        <validity-end-time-local tz="WST">2019-03-28T23:59:59+08:00</validity-end-time-local>
        <next-routine-issue-time-utc>2019-03-22T08:00:00Z</next-routine-issue-time-utc>
        <next-routine-issue-time-local tz="WST">2019-03-22T16:00:00+08:00</next-routine-issue-time-local>
        <status>O</status>
        <service>WSP</service>
        <sub-service>FPR</sub-service>
        <product-type>F</product-type>
        <phase>NEW</phase>
    </amoc>

[adamhsparks]

This would require some effort since the bulletins can be collated country-wide, maybe better as fields in the data itself?