Add Capability term for filter expression restrictions

Extend the term FilterRestriction with an additional property FilterExpressionRestrictions: <Term Name="FilterRestrictions" Type="Capabilities.FilterRestrictionsType" AppliesTo="EntitySet"> <Annotation Term="Core.Description" String="Restrictions on $filter expressions" /> </Term> <ComplexType Name="FilterRestrictionsType"> ... <Property Name="FilterExpressionRestrictions" Type="Collection(Capabilities.FilterExpressionRestrictionType)"> <Annotation Term="Core.Description" String="These properties only allow a subset of expressions" /> </Property> </ComplexType> <ComplexType Name="FilterExpressionRestrictionType"> <Property Name="Property" Type="Edm.PropertyPath" /> <Property Name="AllowedExpressions" Type="Capabilities.FilterExpressionType" /> </ComplexType> <EnumType Name="FilterExpressionType"> <!-- rewrite as allowable values for future extensibility--> <Member Name="SingleValue"> <Annotation Term="Core.Description" String="Property can be used in a single eq clause" /> </Member> <Member Name="MultiValue"> <Annotation Term="Core.Description" String="Property can be used in a single in clause" /> </Member> <Member Name="SingleRange"> <Annotation Term="Core.Description" String="Property can be used in at most one ge and/or one le clause, separated by and" /> </Member> </EnumType> NOTE: the enum should be rewritten as allowable values for future extensibility.