Adds Manage Tags

Summary:
* adds to workspace menu
* adds route
* adds html and scss
* adds service
* adds .json data
* fixes layout of `.list-view__item`

Test Plan:
* load app
* navigate to "Manage Tags"
* confirm that tag data loads
* resize browser for responsive views

Reviewers: rjmackay, spaudanjo, shadowhand

Reviewed By: spaudanjo, shadowhand

Subscribers: sebm90, digitalafrican, eyedol, lkamau, srutto, dkobia

Differential Revision: https://phabricator.ushahidi.com/D391