Add Empty View For Messages, Fixes T465

Summary:  - Add empty view that says `No messages.` when there are no messages to be listed

Test Plan:
 - Go to #messages
 - Go to a tab with no messages
 - See page show an empty view with message `No messages`

Reviewers: shadowhand, rjmackay

Reviewed By: shadowhand, rjmackay

Subscribers: lkamau, srutto

Maniphest Tasks: T465

Differential Revision: https://phabricator.ushahidi.com/D228