PLAT-6499 - Enhance PermissionCheckProvider

Return failures in result object instead of exceptions
Remove live data permission check in Bloomberg impl
(approach was flawed so not worth keeping)
PLAT-6499 - FixUp from PR
PLAT-6499 - FixUp from PR
Merge pull request #61 from OpenGamma/topic/PLAT-6499

PLAT-6499 - Enhance PermissionCheckProvider