DATAJPA-XXX - Add support for dynamically evaluating SpEL expressions in String based queries.

We now support the discovery and dynamic registration of SpEL expression parameters in String based queries. Introduced an ExpressionEvaluationContextProvider that provides access to 
a potentially shared SpEL EvaluationContext that is defined in the application context. This allow shared spring beans to be used within query expressions.
The SpEL expressions are evaluated in org.springframework.data.jpa.repository.query.SpelExpressionStringQueryParameterBinder.potentiallyBindSyntheticParameters(T) by using a hierarchal EvaluationContext with the RootObject set to the current method arguments.
We enhanced the parsing of ParameterBindings in ParameterBindingParser to support "synthetic" Parameters like SpEL expressions that should be evaluated at query time.

This feature works with Hibernate, EclipseLink as well as OpenJPA.

We currently support those variants: 
Indexed parameter:
@Query("select c from Customer c where c.firstname = ?1 and c.attribute1 like ?#{[0] + ' ' + [1]})
To determine the index for the expression parameter we determine the max parameter index present and use that as an offset to generate appropriate parameter indices.

Named parameter:
@Query("select c from Customer c where c.firstname = :firstname and c.attribute1 like :#{[0] + ' ' + [1]})
whereby we generate a name like __$synthetic$__0 for SpEL parameter expression.