* core/providersplit: Split OPC Provider to separate repo
As we march towards Terraform 0.10.0, we are going to start building the
terraform providers as separate binaries - this will allow us to
continually release them. Before we go to 0.10.0, we need to be able to
continue building providers in the same manner, therefore, we have
hardcoded the path of the provider in the generate-plugins.go file
The interim solution will require us to vendor the opc provider and any
child dependencies, but when we get to 0.10.0, we will no longer have to
do this - the core will auto download the plugin binary. The plugin
package will have it's own dependencies vendored as well.
* core/providersplit: Removing the builtin version of OPC provider
* core/providersplit: Vendoring the OPC plugin
* core/providersplit: update internal plugin list
* core/providersplit: remove unused govendor item