vbox: Remove --hostonlyadapter1 option

This option is needed only in --hostonly mode not in --nat mode.

Signed-off-by: Asias He <asias@cloudius-systems.com>
Merge pull request #33 from asias/nic

vbox: Remove --hostonlyadapter1 option
pull: Download hypervisor specific image

Fix 'capstan pull' and related commands to only download the hypervisor
specific image that is going to be used from S3 repository. Github
repositories are still pulled fully because there's no way to partially
clone a git repository.

Fixes #19.

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
s3_repository: Fix downloading a new image

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
install: Add install.bat

Add install.bat for Windows.

TODO: Fix version

Signed-off-by: Asias He <asias@cloudius-systems.com>
vbox: Add Windows support

Note: VBoxManage.exe is not added to %path% by default. User need to add
it. Perhpas we can add it in capstan instead.

Example:
cmd.exe -> capstan run -p vbox vbox.vdi

Signed-off-by: Asias He <asias@cloudius-systems.com>