Uniprot 'sequence variant' features no longer provide a text description of mutation

At some point in the last few uniprot releases, the sequence feature XML has changed to allow residue changes for sequence variant features to be provided as additional elements.

e.g.

<feature type="binding site" description="Substrate" evidence="1">
<location>
<position position="89"/>
</location>
</feature>
<feature type="sequence variant">
<original>M</original>
<variation>L</variation>
<location>
<position position="41"/>
</location>
</feature>

Jalview's uniprot xml parser needs to be updated to show these data in a meaningful way to the user.