New builtins

Enhancements

The Mathics version is checked for builtin modules at load time. A message is given when a builtin doesn't load.
Automatic detection for the best strategy to numeric evaluation of constants.
FileNameJoin now implements OperatingSystem option
Mathics functions are accepted by Compile[]. The return value or type will be Compile[] and CompiledFunction[]. Every Mathics Expression can have a compiled form, which may be implemented as a Python function.
Equal[] now compares complex against other numbers properly.
Improvements in handling products with infinite factors: 0 Infinity-> Indeterminate, and expr Infinity-> DirectedInfinite[expr]
$Path is now Unprotected by default
Read[] handles expressions better.
StringSplit[] now accepts a list in the first argument.
SetDelayed[] now accepts several conditions imposed both at LHS as well as RHS.
Axes for 2D Plots are now rendered for SVGs
InsertBox accepts an opaque parameter

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Pymathics modules now can run initialization code when are loaded.
The builtins list is not hardliked to the library anymore. This simplifies the loading and reloading of pymathics modules.
Decoupling of BoxConstructors from the library. Now are defined at the level of the definition objects. This is useful for customizing the Graphics output if it is available.

A pass was made to improve Microsoft Windows compatability and testing Windows under MSYS.
Include numpy version in version string. Show in CLI
Small CLI tweaks --colors=None added to match mathicsscript.
In the BaseExpression and derivated classes, the method boxes_to_xml now are called boxes_to_mathml.
In the format method of the class Evaluation, the builtin ToString is called instead of boxes_to_text
In order to control the final form of boxes from the user space in specific symbols and contexts.
GraphicsBox now has two methods: to_svg and to_mathml. The first produces SVG plain text while the second produces <mglyph ...> tags with base64 encoded SVGs.