Rename all the datasets in the data catalog in the same manner

[zaleslaw]

And check if it's actually used

Now I see different datasets encoded in URL like this https://github.com/Kotlin/dataframe/blob/master/data/jetbrains%20repositories.csv

Should rename them in the Kotlin manner with camelCase

[Jolanrensen]

Actually, this was renamed on purpose: #356