vbox: Store VMConfig to a file

We can use this file to restart a stopped instance.

TODO: We have duplicated implementation of LoadConfig and StoreConfig.
Need to consolidate and introduce a helper.

Signed-off-by: Asias He <asias@cloudius-systems.com>
vmw: Store VMConfig to a file

We can use this file to restart a stopped instance.

Signed-off-by: Asias He <asias@cloudius-systems.com>
vbox, vmw: Support start an stopped instance

It works like below:

   $ capstan run osv.vmdk
   Created instance: i1397047839

   $ capstan stop i1397047839
   Stopped instance: i1397047839

   $ capstan run i1397047839
   Created instance: i1397047839

Signed-off-by: Asias He <asias@cloudius-systems.com>
vmw: Delete ConfigFile as well

vmxRun deleteVM will not delete the file not created by vmxRun. Delete
it ourself.

Signed-off-by: Asias He <asias@cloudius-systems.com>
vbox: Delete ConfigFile as well

VBoxManage  unregistervm --delete will not delete the file not created
by VBoxManage. Delete it ourself.

Signed-off-by: Asias He <asias@cloudius-systems.com>
cmd/run: Beautify the output when instance is stopped

Before:
   [asias@hjpc capstan]$ capstan run
   Created instance: i1397111888
   OSv v0.06-rc2-31-gdf30ec8

   [/]% [asias@hjpc capstan]$

After:
   [asias@hjpc capstan]$ capstan run
   Created instance: i1397111771
   OSv v0.06-rc2-31-gdf30ec8

   [/]%
   [asias@hjpc capstan]$

Signed-off-by: Asias He <asias@cloudius-systems.com>
Merge pull request #69 from asias/restart2

vbox, vmw: Support start an stopped instance