Adds test case for switch statement on a string
Adds test case for try catch whom rethrow exceptions
Adds test cases to test try catch with resources.
Improves model to discern try normal and try with resource.

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.
Improves model to add multi types for local variable.

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.
Refactors multi catch with a CtCatchVariable/Impl.

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.
Merge pull request #98 from GerardPaligot/support_java7