Bokeh

- integrated bokeh on backend&frontend side (bbossy's changes)
- added example workbook
- started work on "simplification" layer for bokeh-scala (imho poorly documented, please give feedback here -> software design could probably be better... not 100% sure yet on which direction to take). Idea: simplify the 80% tasks/plots data analyst have to do in terms of plots/statistical analysis.
- added spark configurator workbook
If it would extends `DataConnector` (and being generic in its type → we cannot fix it at this level of abstraction), we could use reactive update through `apply` function.