Signed-off-by: Krisztian Litkey <krisztian.litkey@intel.com>

RemoveSpec() can be used to remove a Spec file written
by WriteSpec(). It takes the same name that was passed
to WriteSpec() to create the file.

Signed-off-by: Krisztian Litkey <krisztian.litkey@intel.com>

Add functions for generating ordinary or transient
Spec file names. The generated names can be passed
to WriteSpec() to create the actual Spec files and
to RemoveSpec() to remove them.

Also update the package introduction in the golang
docs describing how dynamic Spec files should be
generated using the API.

Signed-off-by: Krisztian Litkey <krisztian.litkey@intel.com>

Signed-off-by: Krisztian Litkey <krisztian.litkey@intel.com>

This should reduce confusion about how generates Specs
should be written (cache.WriteSpec() vs. spec.Write())
and also reduce the possibility/temptation for users to
bypass the registry/cache when interacting with Specs.

Signed-off-by: Krisztian Litkey <krisztian.litkey@intel.com>

Alias specs.CurrentVersion as pkg/cdi.CurrentVersion.

Signed-off-by: Krisztian Litkey <krisztian.litkey@intel.com>