Add ability to configure machines inside stack definition

[ashumilova]

User configures the machines composing the stack's environment. It can be single machine or multi-machine. The list of machines is collapsible/expendable. By expending a machine, its details and configuration options are displayed,
Each machine have:

• a name
• RAM
• can be defined as dev-machine (meaning it will be the primary machine where Che will injects agents for IDE tooling) (it is a toggle, activating the dev-machine in one machine of the environment will toggle-off in the other machines)
• a list of agents (if selected, they'll be injected in the machine)
• configuration for environment variables
• configuration for ports
• a list of commands

[olexii4]

6d