new: [attribute-type] filename-pattern to describe a filename base on a pattern
new: [attribute-type] filename-pattern to describe a filename base on a pattern

Fix #403

There is no specific validation on the field. This allows us to have a clear
separation between filename and filename-pattern as many users were
using filename for regexp. This also helps the creation of object
template which requires a filename pattern.

SteveClement/MISP,SteveClement/MISP,MISP/MISP,SteveClement/MISP,SteveClement/MISP,MISP/MISP,MISP/MISP,SteveClement/MISP,MISP/MISP,MISP/MISP