Add choice for reading in files of random numbers.

[TorbjornT]

E.g. with

BUBBLE_EFFECTIVE_RADIUS = 1 [logarithmically distributed from 1e-5 to 1e1]

one gets a file called ice_BUBBLE_EFFECTIVE_RADIUS.dat in the Output-dir.

Add boolean random, and then check for existence of .dat files and read the arrays into a dict called something like randomnumbers?

[TorbjornT]

Or possibly check existence of such files, and if present read in and add to runvar attribute.