Use lowercase property names in SpEL examples

[quaff]

According to java code conventions

[sbrannen]

For the record, the proposed changes are to SpEL "property names", not variable names.

As stated in the same chapter:

Case insensitivity is allowed for the first letter of property names.

Thus, person.name, person.Name, Person.Name, and person.getName() are all equivalent with regard to property access in SpEL.

It's ultimately a matter of taste. Some people prefer to follow Java conventions. Others prefer capitalized property names in expressions for improved readability.

In any case, I do think it would be beneficial to focus on Java coding conventions in the examples, with a NOTE pointing out more explicitly what I've stated above.

In light of that, I'll probably merge this PR as-is and add such a note.

[sbrannen]

This has been merged into master in 9c11887 and revised in b01adad.

Thanks