optionally trace theorems used in proof reconstruction

added arithmetic example using div and mod

bump up Nitpick's axiom/definition unfolding limits, because some real-world problems (e.g. from Boogie) ran into the previous limits;
the limits are there to prevent infinite recursion; they can be set arbitrarily high without much harm

merged

comment out debugging code in Nitpick

fixed bug in Nitpick's handling of "The" and "Eps" when the return type is a "bool"

made "NitpickHOL.normalized_rhs_of" more robust in the face of locale definitions

removed "debug := true" that shouldn't have been submitted in the first place

Added derivation and Brouwer's fixpoint theorem in Multivariate Analysis (translated by Robert Himmelmann from HOL-light)

merged