Make constants final classes instead of interfaces

This commit prohibits implementation of the empty interface and
instantiation of the class.  Refer to _Effective Java_ item 19 for
more background.
Migrate InputSupplier callers to ByteSource

A future version of Guava will remove InputSupplier.
Replace InputSupplierMap with Map<K, ByteSource>

A future version of Guava will remove InputSupplier.
Address CheckStyle violations
Replace deprecated calls to LoadingCache.apply
Updating EC2 test mocks to match changes in 79c289d
JCLOUDS-571 - Fix build to suppress maven parent.relativePath warnings at start of build
Fixed format and removed the trailing spaces