Internal: Check if a selected run is STRUCTURE, TESS, MATRIX or TAB file.
checkRuns(files = NULL, warn = FALSE)
A character or character vector of one or more input text files
A logical indicating if a warning be displayed for file those are not STRUCTURE, TESS or MATRIX file.
A character or character vector indicating 'STRUCTURE', 'TESS', 'MATRIX' or 'TAB' for all selected files.