Revise source description (sourceDesc)

[cmil]

In the TEI headers sourceDesc element we currently provide the brief bibl:

<bibl type="digitalSource">
  <name>EarlyPrint Project</name>
  <idno type="URL">https://texts.earlyprint.org/works/A16527_04.xml</idno>
  <availability>
    <licence target="A16527-nc/3.0/deed.en_US">Distributed under a Creative Commons Attribution-NonCommercial 3.0 Unported License</licence>
  </availability>
</bibl>

followed by the biblFull element(s) copied unmodified from the source files.

This is the XSL template currently generating the sourceDesc:
https://github.com/dracor-org/epdracor/blob/3578bf92b61c40d96279e2d303d8b4e3f22dd129/ep2dracor.xsl#L328-L346

[cmil]

@lucagiovannini7 in #54:

Plays have a rich <sourceDesc> with contains both DraCor's <bibl> element (referring to the digital source, i.e. Early Print) and two legacy <biblFull> elements from Early Print (one referring to the original printed source and the other to the digital source for Early Print itself, i.e. the Text Creation Partnership - EEBO/ECCO). See this file as an example. Should we simplify it to align with DraCor standards, while still keeping a reference to previous sources?