Implement functionality to assigne Licenses to Packages and show existing Licenses (#17)

Co-authored-by: Tim Lorsbach <tim@lorsba.ch>
Reviewed-on: enviPath/enviPy#17

templates/actions/objects/package.html

@@ -6,6 +6,10 @@
     <a role="button" data-toggle="modal" data-target="#edit_package_permissions_modal">
         <i class="glyphicon glyphicon-user"></i> Edit Permissions</a>
 </li>
+<li>
+    <a role="button" data-toggle="modal" data-target="#set_license_modal">
+        <i class="glyphicon glyphicon-duplicate"></i> License</a>
+</li>
 <li>
     <a class="button" data-toggle="modal" data-target="#delete_package_modal">
         <i class="glyphicon glyphicon-trash"></i> Delete Package</a>