TcplPlot refactoring

[brown-jason]

• For following code, if we repeat a value in the compare.val this will cause error when potentially not intended. if (!is.null(compare.val) && nrow(dat) != length(unlist(compare.val))) stop("'compare.val' must be of equal length to 'val'")Consider moving after we've loaded all of the data.
• Tcpllegacy needs to be tested/working at some point #250
• Add documentation to tcplPlotUtils
• Style both tcplPlot and tcplPlotUtils
• val should be optional if dat is given (standalone) #249

[cthunes]

added fix for first step in PR