[vector] refactoring api for mask, shuffle creation

[Kharbas, Kishor]

Hi,
I am experimenting with few changes to improve the API. Specifically,

1.       mask and shuffle creation methods (example, maskFromArray()) right now are defined in XxxVector. From user's perspective it seems more intuitive for Mask/Shuffle to define these methods. This patch moves them out of XxxVector to their respective classes.

2.       Moved classes - Species, Shape, Shuffle and Mask, at the top-level instead of being nested inside vector.

Please help me evaluate the changes. Apart from moving methods around and changing signatures, there are changes in Species class -- addition of factory methods to create masks and shuffles.
I am in the process of testing the patch.

Webrev : http://cr.openjdk.java.net/~kkharbas/vector-api/species_refactoring-phase2/webrev-phase2.02/
Javadoc : http://cr.openjdk.java.net/~kkharbas/vector-api/species_refactoring-phase2/webrev_phase-2.JavaDoc.02/jdk.incubator.vector/jdk/incubator/vector/package-summary.html

Thanks
Kishor