Add new flags to hypervisor app management

[jdknives]

Feature description

Two new flags will be added to the VPN with the next release.

• killswitch
• secure

Both accept boolean values. They need to be changeable via the app management interface in the UI.

Reference PRs

• Add killswitch flag, automatic reconnection #608
• Secure VPN #598

[Senyoret1]

I added the options to the UI, but for saving the changes, I need to send the new setting to the PUT /visors/{pk}/apps/{app} API endpoint, which is how the manager currently saves the changes for all app settings. The problem is that the endpoint currently does not accept the killswitch and secure options. After making the endpoint able to receive those settings, I think it will be possible to make the final changes.

[jdknives]

@Senyoret1 just merged #618 so you should be able to go ahead.