Make modify_col_def consistent with other functions

[TymekDev]

Hey! I have been exploring the package a bit and couldn't help but notice that naming on modify_col_def is out of place. What do you think about changing it to set_column_options, update_column_option, or update_column_definition?

Additionally, is there any particular reason why it takes a col_update list over ellipsis (...)? Perhaps it could support both?

[crazycapivara]

@TymekDev Your are absolutely right. The modify_col_def function was made public by accident in the latest dev version.
In the next release there will be a set_column function that allows to set formatters and editors for multiple columns at once. Seel also the PR #59. The ... will then also be supported.