Previously the user was able to set any number to limitThreads UI
component but internally that was reduced to be a maximum of 50 which is
deceiving to the user. Set this is set as a boundary in the UI.
This also fixes a bug that the user could set the number of threads to
zero which follows from GIGO; but let the UI assist by placing a min
number of threads to 1.
implementation dependant although with CPython elements are
unintentionally skipped during iteration.
Basic CPython example:
>>> A = [1,2,3,4,5,6]
>>> for a in A:
... A.remove(a)
>>> A
[2, 4, 6]
