Add bootstrap feature for the design of the diff reports

[tfiedor]

Currently, the design of the diff reports has a fixed design. We need to create a feature, that would allow us to boostrap or change the design based on some parameter.

Mainly provide the following design:

1. Plain: no shading, minimal black/white-friendly colors, minimal animation and interation allowing to view this on paper or e-ink monitors/tables.

[robertvasek]

This has been mostly achieved by the pull request #336 . Possibly adding less animation to the scheme might be the last from this list.