Extract getter/setter/field name mangling from BeanUtil into pluggable AccessorNamingStrategy

[cowtowncoder]

Since there seem to be customizable aspects to how getter and setter implicit names are auto-detected, we should extract current BeanUtil static methods into some kind of pluggable handler, and let that be (re)configured by users (or perhaps by language module(s)?)

[cowtowncoder]

Completed implementation:

• Base api as AccessorNamingStrategy (and matching Provider)
• Configurable standard implementation DefaultAccessorNamingStrategy (along with .Provider thereof)

and latter is configurable regarding getter/is-getter/setter/with-method prefixes, as well as optional validity checking for base name.