Issue: Modules can only open resources as streams

[David M. Lloyd]

Module.getResourceAsStream() is the only way a resource can be loaded 
from a module.  This makes it impossible to do either of the following:

• Determine the size of a resource in advance of loading it
• Determine the existence of a resource without opening it

Loading resources as java.net.URLs allowed these things to be done 
(among other things), however it is also disadvantageous due to the 
heavyweight nature of that class.

I had earlier come up with a simple patch [1], initially as a way to 
address JDK-6865375 [2], which introduced the idea of a Resource class 
that is associated with a ClassLoader, with a name, URL, size, and 
stream factory method, which would also be a clean solution here (though 
with the addition of a Module property as well since in Jigsaw they're 
separate).

The idea is to put resources on a similar footing to classes, whereby 
you can (if suitably permitted) acquire their class loaders just like 
Class.getClassLoader() allows you to do for classes.  This also allows 
things like ServiceLoader to load classes directly from the module which 
contained the corresponding service descriptor.

[1] 
https://github.com/dmlloyd/openjdk-modules/commit/d9ab5a4b51f63d71d0ff5bdb0625ea3fa149f90c
[2] https://bugs.openjdk.java.net/browse/JDK-6865375

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- DML