Add media type, number of rows, duration

[jpmckinney]

media_type:

• [x] BC
• [x] NL
• [x] Halifax reports releasing Excel files (but don't know if XLS or XLSX)

calculated number_of_pages:

• [x] BC (PDF, TIFF)
• [x] NL (PDF)

calculated number_of_rows:

• [x] BC (Excel, CSV)
• [x] NL (Excel)

calculated duration:

• [x] BC