Introduce getAccessEntityTypeDisplayName

Let's add the getAccessEntityTypeDisplayName method to the
PermissionAccessEntityType class.
It returns the localized name (so that you don't have to call tc()) and it
optionally escapes the name in html format, javascript format (default is
to escape in html format).
Fixed wrong translation context
Remove the json encoding option from getAccessEntityTypeDisplayName
Merge pull request #1447 from mlocati/add-AccessEntityTypeDisplayName

Introduce getAccessEntityTypeDisplayName