move example code towards convention of global app

[jwkvam]

For dynamic layouts, the app will need to be global or at least the views will be. I would rather not confuse the matter and encourage the app to be global. As a side benefit, users can then use the listen decorator instead of the subscribe function which should be more readable. This may also allow us to be more compatible with Flask apps if someone wants to have a bowtie dashboard sitting with some other flask stuff.

• refactor example code
• refactor bowtie-demo
• move server.py.j2 functionality into app.py or wherever appropriate.

[jwkvam]

bowtie-demo has been updated