- Fixed NPE in RootPolicyProvider modules

- 

- After removing BaseStaticRootPolicyProviderModule from core API, all
RootPolicyProviderModule subclasses now directly implement
StaticRootPolicyProviderModule

StandardFunction from ID
Renamed StandardEnvironmentAttribute to enum
StandardEnvironmentAttribute
Same thing for StandardCombiningAlgorithms -> StandardCombiningAlgorithm

Fixed non-regression test OW2-22

- Fixed issue #22 (OW2) with non-regression test
- New feature to set Standard Current Time Environment Attribute
(PDP_ONLY, REQUEST_ELSE_PDP, REQUEST_ONLY) with unit tests
- New features: strictAttributeIssuerMatch=false supported when
retrieving attributes from provider modules (if attribute has Issuer,
Issuer-less copy added to context)
- New way of handling ReturnPolicyIdList (return applicable policies)
with new definition of applicable policies (not returning NotApplicable
and enclosing policy is applicable, if any)
-> changes to response in tests IIIG301,302
- Removed TestApplyMarshalling because we consider no longer the
responsibility of the PDP to be able to marshall XACML instances, but
the caller; in particular classes ApplyExpression,
AttributeDesignatorExpression, AttributeSelectorExpression,
AttributeAssigmnentExpressionEvaluator no longer extending JAXB classes
to simplify and improve code memory usage
- New  utility class StandardCombiningAlgorithms for registry of
standard combining algorithms
- New  utility class StandardEnvironmentAttributes for registry of
standard environment attributes
- - New  utility class StandardFunctions for registry of standard
functions
- Fixed issues with autoboxing/unboxing
- Use of Guava Preconditions.checkNotNull() and ImmutableList
- Use of koloboke HashMap/HashSet
- Removed MutableDecisionResult

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