Creates CtTryWithResource/Impl to represent a try-with-resource
and adds posibility to visit it. Improves tests to use the new
interface CtTryWithResource when it used the old one, CtTry.

Creates MultiTypedElement interface and extended by
CtLocalVariable to add the possibility to have multi
types for a local variable. For example, it is used
in multi catch in Java 7: there is one variable and
several types.

Creates a new concept in the model, CtCatchVariable. This
interface defines an exception variable in a catch and can
be visitable. Now, CtCatch are returning a CtCatchVariable
with getParameter and not CtLocalVariable.