add Error handling code

to method configTimeToLiveInSeconds to check the range of $ttl
+ uss hooks
Solve issue #2
Add composeSparqlQuery() and change the const in endpointbase.class.php
uss hooks
queryparser
Merge pull request #4 from OpenISDM-VR/feature_uss_hooks

Feature uss hooks
template method
+ FederatedSearch
Merge branch 'develop' of https://github.com/OpenISDM-VR/X2R into develop
+federatedSearch and other utilities
Merge branch 'develop' of https://github.com/OpenISDM-VR/X2R into develop
Solve issue #5