DATACMNS-535 - Build now requires Java 7 to run.

Remove ‘openjdk6’ from travis.yml.
DATACMNS-533 - Prepare issue branch.
DATACMNS-533 - Infrastructure support for SpEL expressions in manually defined queries.

Extracted SPI build for DATAJPA-564 into Spring Data Commons. Simplified the configuration setup code and removed the ability to define a custom EvaluationContextProvider for now. We directly declare a bean definition which automatically picks up EvaluationContextExtensions.

RepositoryFactory(Bean)Support is now aware of the EvaluationContextProvider to hand it to the template method that creates the QueryLookupStrategy. Deprecated the previously existing template method in favor of an extended one.

Removed variable declarations from the extension interface for now as usually properties serve the same purposes as variables which makes the latter superfluous for now. Applied some JavaDoc and API signature polish. Added unit tests for ExtensionAwareEvaluationContextProvider.

Related pull request: spring-data-jpa#101
Related ticket: DATAJPA-564
DATACMNS-533 - Discover declared functions on EvaluationContextExtension.

We new automatically register public static methods declared on classes extending EvaluationContextExtensionSupport as functions to be used within SpEL expressions.

Related pull request: spring-data-jpa#101
Related ticket: DATAJPA-564
DATACMNS-533 - Discover declared properties on EvaluationContextExtension.

We new automatically register public static fields declared on classes extending EvaluationContextExtensionSupport as properties to be used within SpEL expressions.

Related pull request: spring-data-jpa#101
Related ticket: DATAJPA-564
DATACMNS-533 - Support scoping for functions provided by  EvaluationContextExtension.

Added test case for scoped functions.

Related pull request: spring-data-jpa#101
Related ticket: DATAJPA-564
DATACMNS-533 - Expose special parameters in SpEL expressions.

We now expose special parameters like Pageable and Sort to be used in SpEL expressions if they don't collide with existing named parameters.

Related pull request: spring-data-jpa#101
Related ticket: DATAJPA-564
DATACMNS-533 - Polishing of special parameter handling.

Collapsed variable gathering methods into one, make sure we expose all values (also null ones). Renamed unit test for ExtensionAwareEvaluationContextProvider according to the class name. Some further cleanups in the test case.