Optionally only consider MWL items of a particular Archive MWL AE on coercing received objects against local MWL items

[gunterze]

• if configured

  Name	Type	Description (LDAP Attribute)
  Merge MWL SCP	string	AE Title of external MWL SCP to lookup MWL Item used to coerce request attributes of received objects. (dcmMergeMWLSCP)

  matches an Archive AE Title - or one of its Other AE Titles - do not invoke a C-FIND RQ to the own archive for getting matching MWL items, but directly invoke a SQL query with the specified AE Title as filter in the where clause,

• adjust description of Merge MWL SCP to

  Name	Type	Description (LDAP Attribute)
  Merge MWL SCP	string	AE Title of MWL SCP to lookup MWL Item used to coerce request attributes of received objects. If it refers a MWL SCP of the own Archive Device, the Archive DB is directly queried for a matching MWL item. If it refers an external MWL SCP, that is queried by invoking a C-FIND RQ of the DICOM MWL Service. If absent, the Archive DB is queried for a matching MWL item provided by any Archive MWL AE. (dcmMergeMWLSCP)

Related #428, #3144