Helper function for extractModelParameters. Used to parse each subsection of output within a given file and given results section (e.g., stdyx section) There will be many chunks if latent classes, multiple groups, multilevel features are used.
extractParameters_1chunk(filename, thisChunk, columnNames, sectionName)
A data frame (or matrix?)
name of Mplus output file being processed
character vector of output chunk from which to extract parameter values
character vector of expected column names for output chunk