Finish internationalisation

See merge request !149

# Conflicts:
#   internewshid/hid/templates/hid/tabs/filters/age_range.html

Age range support

See merge request !150

Fix table numbering logic

See merge request !144

Also adds support for filtering messages by one term or another

See Shttps://aptivate.kanbantool.com/b/437721-internews-hid-2018#27567031.

Fix edit screen formatting

See merge request !148

Remove external_id from table view and filters

See merge request !143

Rename "Source" to "Collection Type"

See merge request !142