Redesign of `TaylorSeries.jl` to add N-variable expansions

I have moved the contents of TaylorSeries.jl to `utils_Taylor1.jl`
which now includes everything related to 1-variable Taylor expansions.
I created `utils_TaylorN.jl` which will include everything
related to N-variable (N>1) Taylor series.
Changes in utils_TaylorN.jl to automatically regenerate coeffsTable
Small changes in TaylorSeries
Operations added
Changes in exported functions for TaylorN; square is not imported (deprecated)
Cosmetic changes
Corrected an error introduced in the last commit (copy-paste)
Corrected another bug introduced in
Added const functions for TaylorN

Defined some constant values: MAXDEG, NUMVARS

The hash table (generateCoeffsTable) and its size are defined as constants

Added function that returns key in the dictionary, corresponding to
some indices

Corrected multiplication; added division, and power of Int
Added power to real and sqrt
sincos redesigned to return a tuple and not depend on string
Added sin and cos for TaylorN
Changes in ; it returns now both sin and cos Taylor functions
Added diffTaylor function, which returns the partial derivative
Simplified code by adding the functions posIniFinK and posIniNumFinK
Changes in names of consts and hash tables; hash tables are all dictionaries
Added function `definiteIntegralTaylor`; not yet exported
Added the functions rem, mod and mod2pi
Added `pretty_print` and adapted `showcompact` to it

I added `pretty_print` along what David did, for both Taylor and
TaylorN, and adpated showcompact to use it. The output is still
the default one. These and related functions were moved to
TaylorSeries.jl, because some functionality is shared.
Expanded evalTaylor (Taylor and TaylorN) and also ^ (TaylorN)

evalTaylor can now evaluate a Taylor on a TaylorN, i.e., an implementation
of the composition for Taylor. For TaylorN it evaluates the polynomial
on a vector of coefficients, or also on a vector of Taylor variables.
The latter is implemented on `TaylorSeries.jl`, since it requires that
both utils_Taylor1.jl and utils_TaylorN.jl are loaded.