JCLOUDS-410. Deprecate Payload.getInput

We plan to transition Payload to ByteSource in the next major release.
Unfortunately Payload.getInput masks its checked exception and
ByteSource.getInput is final so we cannot continue to mask the
exceptions.  Deprecation of getInput and addition openStream allows us
to transition callers from the former to the latter.
JCLOUDS-410. Add support for ByteSource Payloads

Also deprecate byte[], File, InputSupplier<InputStream>, and String
Payloads.  Callers should instead provide a ByteSource via
ByteSource.wrap(byte[]) and Files.asByteSource(File)
Address Checkstyle violations
JCLOUDS-399: Deprecate BlobBuilder.calculateMD5

Callers should instead call BlobBuilder.contentMD5, usually with the
results from Guava Hashing.md5().  This narrows the API and removes a
strange IOException from callers.
JCLOUDS-401. Make BlobName Function type-safe
Fixing rackspace-clouddatabases-{us,uk} openstack-trove dependency groupIds
Switch to maven-compiler-plugin 3.1
JCLOUDS-410. Correctly override getInput

Payload.getInput must always call openStream to handle overridden
methods correctly.  Previously this caused errors in jclouds-chef in
BaseCipherPayload.