Add clearAllTokens() to TokenStorageInterface and improve its comments.
Implement clearAllTokens and fix clearToken in Memory storage.
Implement clearAllTokens and fix clearToken in Redis storage.
Proper writing in a comment.
Implement clearAllTokens and fix clearToken in Session storage.
Implement clearAllTokens and fix clearToken in SymfonySession storage.
Fix potential deletion attempt on non-existing variable.
Minor storage fixes and test fixes to accommodate the new clearToken method.
Merge pull request #80 from borfast/fix_clear_token

Fix TokenStorageInterface::clearToken()