Changes

Align JSP spec with Import changes added in EL 3.0 (#205)

* Part of the fix for #44

The EL environment is now explicitly aligned with the scripting
environment. Note that several implementations have already implemented
this on the basis that the requirement was implied. The following has
now been made explicit:
- the implicit/default imports defined in the JSP spec apply to the
  EL environment as well
- imports declared via the import attribute of the page directive also
  apply to EL

* Fix a comment typo

* Complete the implementation of #44

Refactor ScopedAttributeELResolver into two additional resolvers
(ImportELResolver and NotFoundELResolver) to remove the special handling
for those cases that was unrelated to scoped attributes.