Change size of the **volume** and file system. If there is no file system, only
the **volume** itself will be resized. You can specify a **device** to add into
the **volume** pool prior the resize. Note that the **device** will only be added
into the pool if the **volume** size is going to grow.

If the **device** is already used in a different pool, then **ssm** will
ask you whether or not you want to remove it from the original pool.

In some cases, the file system has to be mounted in order to resize. This will
be handled by **ssm** automatically by mounting the **volume** temporarily.

In addition to specifying new size of the volume directly, percentage can be
specified as well. Specify **--size 70%** to resize the volume to 70% of it's
original size. Additionally, percentage of the used, or free pool space can
be specified as well using keywords FREE, or USED respectively.

Note that resizing btrfs subvolume is not supported, only the whole file
system can be resized.
