v2 Re-implement the dobj class

[ZogopZ]

Use icoscp_core to completely rewrite the Dobj class (following the old Dobj class return types) for version 2 of icoscp. The following projerties/methods are to be re-implemented:

• [x] Dobj.info
• [x] Dobj.meta
• [x] Dobj.citation
• [x] Dobj.get_citation(format)
• [x] Dobj.licence
• [x] Dobj.previous
• [x] Dobj.next
• [x] Dobj.colNames
• [x] Dobj.variables
• [x] Dobj.data
• [x] Dobj.get(variables)
• [x] Dobj.getColumns(variables)
• [x] Dobj.dobj = PID
• [x] Dobj.id = PID
• [x] Dobj.valid
• [x] Dobj.lat
• [x] Dobj.lon
• [x] Dobj.elevation
• [x] Dobj.alt
• [x] Dobj.station
• [x] Dobj.size()
• Dobj.dateTimeConvert (is not going to happen)