JCLOUDS-625: Set VolumeBuilder id to nullable in VolumeImpl

VolumeBuilder does not allow null id while VolumeImpl allows it to be nullable.
Improve use of ByteSource
Reduce Swift integration test input size

Previously testMultipartChunkedFilenames uploaded 55 MB and now it
uploads 5 MB.
[JCLOUDS-474] refactor SoftLayer support
JCLOUDS-40: Unasync Rackspace Cloud Identity
JCLOUDS-622: Remove most vestiges of InputSupplier

Guava 16 deprecated InputSupplier and a future release will remove it.
JCLOUDS-549: Fix NPE in LoginCredentials.toString

- also deprecates LoginCredentails.get(Password|PrivateKey)
- use getOptionalPassword and getOptionalPrivateKey instead
JCLOUDS-622: add Strings2.toString(InputSupplier)

We did not deprecate this in 1.7.x as previously thought.
Address Checkstyle violations
Close streams in integration tests

Also remove bogus delete workaround.  Previously unclosed
FileInputStream caused test failures on Windows which cannot delete
open files.  Found with Kohsuke's file-leak-detector.
Enable more filesystem integration tests

Other tests will require Java 7 xattr support.
Replace const.txt file input with synthetic inputs

This commit replaces file resource-based test inputs with in-memory
equivalents.  This is more consistent and efficient than the previous
approach.  Also resized some test inputs to be partSize + 1 instead of
2 * partSize.  Tested against aws-s3, blobstore, core, cloudfiles-us,
and filesystem.
JCLOUDS-554: Update Nova default API to v2