A S4 class for the Category level result of an Intensity analysis.  Can be
plotted with the plot method plot.
The slots categoryData and categoryStationarity can receive
   tables for "Gain" or "Loss" in the following format:
Gain
categoryData: <tibble>. A table containing 6 columns:
Period: <fct>. The period [Yt, Yt+1].
To: <fct>. A LUC category j.
Interval: <int>. Duration of the period [Yt, Yt+1] in years.
GG_km2/GG_pixel: <dbl>/<int>. Area of gross gain of category
   j during [Yt, Yt+1].
Gtj: <dbl>. Annual intensity of gross gain of category j
   for time interval [Yt, Yt+1].
St: <dbl>. Annual intensity of change for time interval [Yt, Yt+1].
categoryStationarity:  <tibble>. A table with the results of a
 stationarity test of the gain of the categories on the Category level, containing 5 columns:
To: <fct>. A category of interest j.
gain: <int>. Number of times a category had gains during all
   time intervals [Y1, YT].
N: <int>. Total number of evaluated time points (T).
Stationarity: <chr>. Active Gain or Dormant Gain.
Test: <chr>. Y if stationarity was detected and N if not.
Loss
categoryData: <tibble>. A table containing 6 columns:
Period: <fct>. The period [Yt, Yt+1].
From: <fct>. A LUC category i.
Interval: <int>. Duration of the period [Yt, Yt+1] in years.
GG_km2/GG_pixel: <dbl>/<int>. Area of gross loss of category
   i during [Yt, Yt+1].
Lti: <dbl>. Annual intensity of gross loss of category i
   for time interval [Yt, Yt+1].
STt: <dbl>. Annual intensity of change for time interval [Yt, Yt+1].
categoryStationarity: <tibble>. A table of stationarity test
  over the loss of the categories in the Category level, containing 5 columns:
From: <fct>. A category of interest i.
loss: <int>. Number of times a category had losses during all
   time intervals [Y1, YT].
N: <int>. Total number of evaluated time points (T).
Stationarity: <chr>. Active Loss or Dormant Loss.
Test: <chr>. Y if stationarity was detected and N if not.
lookupcolorThe colors (character vector) associated with the LUC legend items.
categoryDatatibble. A table of Category level's results (gain (Gtj) or loss (Lti) values).
categoryStationaritytibble. A table containing results of a stationarity test. A change is considered stationary only if the intensities for all time intervals reside on one side of the uniform intensity, i.e are smaller or bigger than the uniform rate over the whole period.