Update Link to App Catalog Repository on Index Page
Update Link to App Catalog Repository on Index Page

Updated the link to the App Catalog git repository
and fixed a minor typo in the TOSCA template section

Change-Id: I64f603457f123ff77d04fc2ef1290e728df17746

stackforge/apps-catalog,stackforge/apps-catalog,stackforge/apps-catalog,stackforge/apps-catalog