Consolidate usage of "conference data" json documents

[kwsutter]

This Issue is in response to a comment from @heiko-braun in my recent PR #157:

"@kwsutter I wonder if it would be better to retrieve the bootstrap data (speakers in this case) from the demo-boostrap module, like in https://github.com/eclipse/microprofile-conference/blob/master/microservice-schedule/src/main/java/io/microprofile/showcase/schedule/persistence/ScheduleDAO.java#L55. This could replace the usage of yet another dataset (ConferenceData.json) in the speaker-service. Or do i miss something?"

I agreed that this type of consolidation or re-use of existing json documents would be a good idea, but it was beyond the scope of the IP clean up Issue #154 that I was pursuing. Thus, the creation of this new Issue.

[carlosdlr]

Hello kwsutter, my name is carlos de la rosa and i'm new in the community and i saw that you are requesting help on this, if you consider i can help you.

Thank you