fit_DFA: Fit DFA to timeseries datasets
In jpwrobinson/funk: James Robinson's functions, attributed where stolen

This builds on DFA tutorial here: https://nwfsc-timeseries.github.io/AFTSLabbook/sec-dfa-plot-data.html

1	fit_DFA(df, proc = 3, id, plot = TRUE, yr_frst, yrlast, clr = clr)

`df`	is a matrix of time series
`proc`	is the number of underlying processes, defaults to 3
`id`	is the name of each time series
`plot`	specifies whether fits and loadings should be plotted, defaults to TRUE
`clr`	is a vector of colours applied to each time series if plot = TRUE
`yr_first`	is the first year of the time series
`yr_last`	is the last year of the time series