This patch introduces a new parameter --all for the remove
command of the box plugin. Setting this parameter will remove
all available versions of a specific box.
Example usage:
```
$ vagrant box list
ubuntu/trusty64 (virtualbox, 20150427.0.0)
ubuntu/trusty64 (virtualbox, 20150430.0.0)
ubuntu/trusty64 (virtualbox, 20150506.0.0)
```
```
$ vagrant box remove ubuntu/trusty64
You requested to remove the box 'ubuntu/trusty64' with provider
'virtualbox'. This box has multiple versions. You must
explicitly specify which version you want to remove with
the `--box-version` flag. The available versions for this
box are:
* 20150427.0.0
* 20150430.0.0
* 20150506.0.0
```
With the --all parameter it is possible to remove all versions at once.
```
$ vagrant box remove --all ubuntu/trusty64
Removing box 'ubuntu/trusty64' (v20150506.0.0) with provider 'virtualbox'...
Removing box 'ubuntu/trusty64' (v20150430.0.0) with provider 'virtualbox'...
Removing box 'ubuntu/trusty64' (v20150427.0.0) with provider 'virtualbox'...
```