Optimize compilation of MVEL expressions

Some MVEL expressions are compiled without any parsing context, which is an issue for performance.

The documentation at http://mvel.codehaus.org/MVEL+2.0+Typing explains how to configure this.

Problem is visible in MvelExpression#eval and MvelTemplate#eval for instance, as the expression is compiled there without any context:

MVEL.compileExpression(expr);

TemplateCompiler.compileTemplate(expr)

Other parts of the code might need the same optimizations, like the ones in class scripting:

public static MvelScript compile(String script) {
    return new MvelScript(MVEL.compileExpression(script));
}

Scripting#newExpression and Scripting#newTemplate methods would also need to be updated, API changes will be required.