JCLOUDS-653: Upgrade to Guava 18.0-rc1

Release notes:

https://code.google.com/p/guava-libraries/wiki/Release18
JCLOUDS-653: Address Guava 18 deprecations

Mostly renaming Objects.toStringHelper to MoreObjects.toStringHelper.
Correct license headers
Remove maven-license-plugin

This never seemed to work and we will enforce license text via
Checkstyle instead.
JCLOUDS-653: Upgrade to Guava 18.0

Release notes:

https://code.google.com/p/guava-libraries/wiki/Release18
Add whitespace after semicolons
Remove spurious whitespace
Prevent instantiation of utility classes

Also prevent extension.
Remove redundant modifiers from interfaces
Avoid primitive wrapper constructors
Address FindBugs warnings
Address Checkstyle violations
Replace uses of ByteArrayPayload
initial support for Virtustream xStream API
wip