Allow microfactory to be used as a package

In addition to running with `go run` and creating a microfactory binary,
allow microfactory to be used as a package from other go tools as well.

To allow other packages to use this, it needs to be in a non-main
package, but `go run` requires a main package. So microfactory.bash runs
a sed script before running microfactory with `go run`.

This could also be solved by using a relative import, but neither
blueprint nor microfactory currently support that.

Change-Id: I084163b14720102b3fb93a3c9d44b5d0225ff2c8