FilterConllRows: Filters a tibble representing a sentence and returns matches
In utacorpora/depsearcheR: Analyze Conll Annotated Data in R

Filters a tibble representing a sentence and returns matches

1 2	FilterConllRows(tab, column_name, column_val, use_regex = F, is_negative = F)

`tab`	a conll represented sentence as a tibble OR a string representation of the sentence which will be converted to a tibble
`column_name`	e.g. POS, lemma
`column_val`	what the value of the column should be, e.g N, igrat'
`use_regex`	if false, exact matches will be searched, if true, regexes
`is_negative`	if True, will filter only rows NOT matching the condition