Duplicated theme_drwhy*

[pbiecek]

Currently in the shapper we have hard copies of drwhy themes

> library("shapper")
Attaching package: ‘shapper’
The following objects are masked from ‘package:DALEX’:
    theme_drwhy, theme_drwhy_colors, theme_drwhy_vertical

maybe we can use directly themes from DALEX package?
as it is done in iBreakDown
https://github.com/ModelOriented/iBreakDown/blob/master/R/plot_break_down.R#L25

this way we will not need to maintain separate copies of theme_*

[maksymiuks]

Done, thanks :)