Use sessionsStorage for copied content

[dnwhte]

No description provided.

[mattbrailsford]

Changes look good but a couple of extra things are needed:

1. If we aren't using localStorageService then there is no need for it to be injected as a dependency.
2. Need to update the canCopyContent / canPasteContent methods to check session storage is available rather than the local storage service (I dunno if it's possible that local storage is supported but session storage isn't, but either way, it should probably consistant)

I'm not as precious about the following idea, but thought it worth sharing (@leekelleher maybe you have some thoughts):

I wonder if creating our own storageService might be a more robust approach here. Internally this could use the umbraco localStorageService and check to see if sessionStorage is supported. If not, use our own implementation, but if it is, then use cores. This way it's kinda self upgrading and keeps all the storage code in a single location.