A right object with like level will not be displayed in page administration

FTM, the Like right is named `Like`, with first letter uppercase (as we can see it here). However, the rest of rights that exists in the platform have lowercase name, as it's implemented here.

Consider the following use case:
1. Go to the WebPreferences of a space
2. Edit the page in object mode
3. Add an object of type XWiki.XWikiGlobalRights. For that object, set the level to `Like` and whatever strategy for it (allow/disallow).
4. Go to the WebPreferences of the space

Expected result: in the table of the rights, `Like` is checked (whether it's set on allow/disallow).

Actual result: `Like` is not checked

What's happening behind the scene: the `Like` column from the table where rights are displayed expects a value of `like` for the levels field, in order to display the checkbox filled.

Going backwards, if `Like` checkbox is filled from the administration's rights view, the levels field will have `like` value in the object, so if the user views the page in editor=object, the `like` will not be filled in the dropdown.