Refactor reference collection process

Refactor reference collection process of JFormatter.
Rename predicate-methods to more understandable and correct names.
Rename `collisions` to `isAmbiguousIn`.
Rename `supressImport` to `isImplicitlyImported`
Introduce new `isImportable` predicate.
Inner classes import fix.

Do not import inner classes of currently generated classes.
Such inner classes can be private!
Try to import outer class when it's impossible to import inner class itself.
Do not import inner classes most of the time.

Import inner classes only
when inner class' name contains outer class'name,
like in `LinkedList.LinkedListNode`.

Use explicit references and do not import inner classes in
all other cases.
Fix prefix/postfix operator distinction
Merge pull request #6 from sviperll/master

Some bug fixes and some slightly questinable changes.