WIP on-screen error messages for Lumin - #126

WIP: Just added SpatialLogger which purpose would be to render spatial log messages.
Next: Add capabilities to open a prism which loads all the log messages sent to the SpatialLogger. The idea is to have spatial console.

Testing with src/configuration.js having showSpatialLogger: true throws:
Fatal signal 11 (SIGSEGV), code 1 ... (index.js) which is an exception while invoking:
app.requestNewPrism([1.0, 1.5, 0.2])
Requires further investigation.

The reason for the exception has been identified: requestNewPrism() must be executed from within BaseApp.onAppStart().

In order to activate the SpatialLogger the developer needs to add configuration for the logger prism to lumin/main.js file:

const spatialLogger = {
    size: [0.5, 1.0, 0.2],
    position: [-1.0, 0, 0],
    orientation: [0, 0, 0, 0]
}

mxs.bootstrap(<MyApp type='landscape' timeDelta={0.5} spatialLogger={spatialLogger}/>);