Maps an input file name to an output file name according to a
very simple pattern rule inspired by "patsubst" from "make".
A SimpleFilePattern is constructed giving two(2) Strings which contain exactly
one(1) place holder character. Then it is applied to some input String, yielding
the output String.
patterns = inpre%inpost
inputname = XXXXinpreYYYYinpost
(with inpost = latest occurence of inpost, inpattern must even END WITH inpost.
inpre = latest occurrence in inpattern, before inpost)
outputname = XXXXoutpreYYYYoutpost
stem = YYYY
// ?????? inpre or outpre may be empty, but not both.
As a variant, there is the case "multiple=false", in which neither of the Strings contains
a place holder character. In this case the input must be identical with the first
string to yield the second.
LATER a variant with an additional variable suffix could be sensible:
inputname = XXXXinpreYYYYinpostZZZZ
(with inpost = latest occurence of, inpre = latest occurrence before inpost)
outputname = XXXXoutpreYYYYoutpostZZZZ