[vector] RFR -- removing Shape as type parameter

[Brian Goetz]

The below patch (tests pass) removes the Shape type argument from Vector 
and subtypes.

     http://cr.openjdk.java.net/~briangoetz/panama/noShape.patch

The use of Shape as a generic type parameter is clever, in that it does 
a good job of providing compile-time type safety (preventing us from 
mixing vectors of the wrong species), but I think we might be pushing it 
too hard here, and I think it can be profitably removed. It is rare to 
be mixing vectors who have the same element type but different shapes; 
when we do, these can (and must) be caught by runtime checks (regardless 
of whether we’re using static type checking to minimize the risk of 
mixing vectors of incompatible sizes, we still have to check that things 
match in the implementations (as the user could be using erased types.)  
The Shape parameter bubbles out into the user code, for relatively 
little benefit.  I don't think it carries its weight.

Removing the Shape parameter also lets us undo another distortion, which 
is making the Shape constants into separate classes.  Now they can be a 
regular enum.  (Similarly, this also clears the way for some downstream 
improvements to the API.)

(The patch is large as it includes the changes to the generated files 
and tests, but all changes were made to the underlying templates.  
Here's a smaller patch, which only contains changes to the source 
templates and non-templated source files, in case that's easier to review.)

http://cr.openjdk.java.net/~briangoetz/panama/noShapeSourceTemplatesOnly.patch