Issue #110 - Made GUI port optionally configurable

[robschneider16]

Instead of defaulting to port 8080, the ait gui should now look at the
ait config and pull the defined gui.port number from there if its defined.
If it is not defined, then it will use the default of 8080. All of which
gets overwritten if the user provided a port number to the init method

[MJJoyce]

Hey @robschneider16, thanks for the pull request. The changes here definitely cover the functionality we need but there's a bit of a change in our config layout now that we've switched over to the new server architecture. The init function in the GUI is leftover from the "old API" and Plugins can be passed additional configuration arguments beyond the required attributes. The gui.port attribute (really all the old GUI config stuff) isn't going to stick around in the future since we expect all necessary config for a Plugin to be defined under that Plugin's initialization block.

plugins:
    - plugin:
        name: ait.server.plugins.ait_gui_plugin.AITGUIPlugin
        inputs:
            - log_stream
            - telem_stream
        outputs:
            - command_stream
        other_parameter: anything_you_need

Here, other_parameter is not a required parameter and will be accessible in the Plugin's __init__ function via kwargs. I would suggest updating the Plugins __init__ to pull a parameter called port from kwargs and pass that to the gevent.spawn(self.init) call. That will get us the functionality we need and when we clean up this Plugin and (likely) drop init we'll have to change less.

Thoughts?

[MJJoyce]

I realize that it's not a problem in this instance but we should avoid hasattr in 2.x in my opinion. Of course, we're moving to 3.x shortly and it won't matter at all but sticking with try ... except here in 2.x is safer in the general case (it's also the same number of lines in this example). I also realize this is already present in the code so I don't blame you much =D. Don't need to change it, just a general comment for future consideration.

Soap boxing aside, isn't getattr cleaner here or is there a reason for the expanded check?

port = int(getattr(self, 'port', 8080))

[MJJoyce]

I think a typo snuck in here @robschneider16

host = getattr(self, 'port', 'localhost'):

should be

host = getattr(self, 'host', 'localhost'):

[MJJoyce]

Thanks @robschneider16!!