Make imports prefer the "current" package

[Mercerenies]

If a module import is ambiguous and one of the candidates is in the same package as the importing module, the module with the same package should be favored over the others. This behavior will only apply if the short form of use is used; in the long form fromPackage, the package name is already being specified by the user.

To this end, we may have to define a dynamic $currentPackage variable or similar, so that the import mechanism can query for the current package. Alternatively, we could attempt to use metaprogramming tools to get at the enclosing module (possibly exploiting $whereAmI to do so).

[Mercerenies]

d4d64ca is not a full fix, but it does improve the situation somewhat by eliminating a lot of ambiguity errors.