BibRecord: new MARC code filter

* Filters a record based on MARC code

* Supports wildcards in identifiers and subfield code

Signed-off-by: Patrick Glauner <patrick.oliver.glauner@cern.ch>
BibFormat: new 'xmf' format

* Supports filtering per MARC tag, identifier and subfield

Signed-off-by: Patrick Glauner <patrick.oliver.glauner@cern.ch>
Merge pull request #31 from pglauner/master-xm-fielded

Master xm fielded