Tainers::Specification basic operations

Tainers::Specification class represents the specification for a
(always) named container, with parameters passed through to
Docker::Container::create as needed to ensure existence.
Work around state manipulation bug

The Docker::Container::create method pops the 'name' attribute
off its options, which means it mutates the params we pass to
it.

So now we pass it a copy of the params instead of the original
params hash.