function for collapsing text vectors
default method for text_collapse()
text_collapse() mehtod for list
text_collapse() method for data.frames
text_collapse() method for matrix
text_collapse(x, coll = "")# S3 method for default
text_collapse(x, coll = "")
# S3 method for list
text_collapse(x, coll = "")
# S3 method for data.frame
text_collapse(x, coll = "")
# S3 method for matrix
text_collapse(x, coll = "")
object to be collapsed
separator between collapsed text parts