Use of CacheKeys in plots and tables

[cabaJr]

Re-implement the use of cache keys to compare new requests for plots. When the generate button is pressed on a plot selection, the code should compare the hash (generated with digest::digest(x, "xxhash64") ) of the settings previously sent, with the hash of the new settings.

If the two cache keys are identical, do not recompute the plot but re-load the previous one. Need to create a function that creates the hash key given the plot setting and dataset. if the dataset is changed (i.e. new files are added, not supported at the moment) the key should be invalidated as there is a new cacheKey for the dataset

create the function in Annotate and it should compare the cacheKeys of "Dataset", and "parameters" (including plot type, data range if subsetting data, ids, etc)