BUG FIXES
jitter in TIS() and simulate_background_cells().SIGIFICANT USER CHANGE
simulate_background_cells() added an option (method = "Even") to simulate evenly spaced background images. This change is accompanied with addition of two parameters, method - to choose the background cell distribution and jitter
TIS() were modified accordingly.SIGNIFICANT USER CHANGE
plot_image to simulate_background_cells().NEW FEATURES
utils.R file to store internal functions.SIGNIFICANT USER-VISIBLE CHANGES
SingleCellExperiment to SpatialExperiment.Phenotype to Cell.Type.