Direct execute

convert `execute` command `container` arg to optional  `--container` argument

if `zpm execute zapp_path.zapp` is invoked the zapp will be executed directly without deploying
if `zpm deploy zapp_path.zapp --execute` is invoked zapp will be deployed and then executed
if `zpm execute zapp_path.zapp --container container_name` is invoked an already deployed zapp will be executed

I think the last one should become `zpm execute swift://./container_name/zapp_name.zapp` instead, but lets leave it for now
When I try this, I get an error.

```
$ zpm execute hello.zapp
Must specify Content-Length
```