Don't halt `project dev` command if the sandbox is already running

[alansemenov]

Currently project dev command halts with message "Sandbox ... is already running", if the project's sandbox is already running.
We should allow this to support cases when users want run the sandbox in a separate terminal window to access the xp logs.

1. Store sandbox mode (dev or standard) in .enonic file once the sandbox is started
2. If the sandbox is running when project dev command is executed, check sandbox mode.
3. If it's dev, proceed to starting the dev command.
4. If it's not dev, show message "Restart sandbox ... in development mode to allow execution of dev command" and halt the dev command