Provide user defined port and proj defaults

[IvayloG]

Closes #271

Additional information related to this pull request:

via prompt session:

• The user is provided an option to choose a port. If passing something else than a number, he should provide a new one or choose the suggested default one (pressing Enter).

via ig start command:

• The user can pass a port like: ig start --port=1234. If passing something else than a number, the project will be served via the default port for the framework/project type specified in the ignite-ui-cli.json.

[coveralls]

Coverage decreased (-0.3%) to 88.362% when pulling c12aef1 on IGanchev/choose-port into 8551c98 on master.