GLASSFISH-21148 Fixed parsing principal from metadata

- prinicpal was parsed, but metadata were not updated
GLASSFISH-21148 More descriptive exception messages
GLASSFISH-21219 Using HashMap instead of HashSet

- Session.hashCode may change (serializable)
GLASSFISH-21219 Using HashMap instead of HashSet (HA/SSO)
GLASSFISH-21146 Fixed NPE in log

- avoid toString call (implicit and safer for null values)
- debug replaced with logging level FINE
Merge pull request #47 from dmatej/GLASSFISH-21146

GLASSFISH-21146 Fixed NPE in log
Merge pull request #45 from dmatej/GLASSFISH-21148

Glassfish 21148 - fixed bug in SSO clustered session management
Merge pull request #46 from dmatej/GLASSFISH-21219

Glassfish 21219