PropertyClass#getFieldFullName() should prefix the meta property name with the property type

ATM if you call PropertyClass#getFieldFullName() for the "editor" meta property of the TextArea property type you simply get "editor". This makes it hard to translate meta properties because the translation keys are too generic and can collide with existing keys..

For instance, if you want to add a hint for the editor meta property of the TextArea property you have to translate "editor_hint" ATM.

I propose to change getFieldFullName() to prefix the meta property name with the property type. Of course, the behavior for object properties shouldn't change. ATM we don't have any translation keys for meta properties but there is a chance (very low IMO) that some XWiki users have translated meta properties using the current key format (this format is hidden in the code so I doubt it) so the proposed change could break those translation keys. Nevertheless, I see this issue as a bug so I strongly believe we should fix it.