Make EventBus Timeout Configurable

[kkoz]

Fixes #37
See github.com/glencoesoftware/omero-ms-image-region/pull/160

This PR is mostly for consistency with omero-ms-image-region in allowing the configuration of the EventBus send timeout in the config.yml file.

Testing

This one is trickier to test. The only ways I've succeeded are:

1. Add a sleep line in the code
2. Import a test image like 'test&sizeX=2304&sizeY=2304&sizeZ=12&sizeC=3&pixelType=uint16&sleepOpenBytes=500.fake'. Note the image ID. Then the very first call to webclient/render_birds_eye_view/<image id>/96 will trigger the sleep. Set your config accordingly to induce the timeout.

[sbesson]

Tested using the sample synthetic file as glencoesoftware/omero-ms-image-region#160 (review) and the webclient/render_thumbnail/size/<size>/<id>/ endpoint.

When using a thumbnail size that has not already been generated, the render call exceeds the default 15s timeout (3 channels with a 5s delay per channel) and results in a 500 error. Re-running the same request returns immediately. Increasing the timeout to 20s via the configuration allows to request a thumbnail of different size without hitting the micro-service timeout.