Fix <processinfo> parsing for EAD

Conflicts:

	apps/qubit/modules/object/config/import/ead.yml
Fix start/end date in EAD <unitdate> ref#6222
Fix YYYYMM date parsing refs #6222
Added physical facet to physdesc EAD import
Fix physdesc import in EAD refs #6426
remove superfluous <lb/> in EAD export
Fix tools:run context issue
Improved processinfo for EAD
Fix link to external assets in showDownloadComponent, fixes #6548

This moves the construction of a public URL into an instance method on
QubitDigitalObject, so consumers like showDownloadComponent don't
need to actually care whether the target is local.