Display the "Create a new space" link for users with the right to create a space

Steps to reproduce:

1. Login with a normal (non Admin) user
2. Use the Add menu to create a new space
3. Check the Spaces macro from the homepage -> there's no button to create a new space even if you have this right

This issue can be fixed by changing the code from the Spaces macro (http://localhost:8080/xwiki/bin/edit/Main/Spaces?editor=object&classname=XWiki.WikiMacroClass&object=0) where the rule for the button to appear is "## Only if the current user has admin rights and the current action is not inline.".

We need to change this as it's possible for an user to have the right to create a space without being an Admin.