[make:entity] managing keyword prefixes (is, has) for boolean properties getters

[ClemRiviere]

• Refactoring the getter prefixes for make:entity
• Introducing exceptions for boolean fields : not adding the prefix to getter name if field begins with "is" or "has"

Related to #1492

[nicolas-grekas]

This change makes sense to me. It's consistent with the autodetection of the type (boolean) when asking for the type.
I'd suggest doing the same for setters, but only for the "is" prefix: isInternational property => setInternational. (but hasColor => setHasColor)

[jrushlow]

This looks pretty good @ClemRiviere! - 1 minor comment. Also if you're up for doing the same for addSetter() as @nicolas-grekas suggested, that would be even more awesome!

[jrushlow]

Thanks @ClemRiviere!