Creating about page #293

Tabs for "What is HDX" and "Data Licenses"
Merge remote-tracking branch 'origin/preDev' into
preDev-alex-general-changes

Conflicts:
	ckanext-hdx_theme/ckanext/hdx_theme/public/hdx_theme.css
Merge remote-tracking branch 'origin/preDev-alex-general-changes' into preDev