Simplify workflow using Arrow C++ library in R

[damianooldoni]

As this issue has been solved (inbo/inborutils#42), we can avoid the two table step. This will reduce a sensible portion of the time used to generate the cubes.

This will affect the creation db script, both for BE and EU.

[damianooldoni]

This didn't work properly. But I will try to switch from SQLite strategy to Arrow.