[UPD] Enforce C++ version and improve setup.py flexibility

Context

1. C++-14

Fixes #225 (closed) for aidge_core. The same update must be done on every module.

2. Python module compilation

Also increase setup.py compilation option flexibility using environment variables. Made to work with aidge!97 (merged)

3. log format with spaces and newlines

'\n' and ' ' characters at the beginning of line are not ignored anymore in Log::log function

For example, let's have

>>> s = f'my results:\n\n    value 1: xxx\n\n    value 2: xxx'
>>> print(s)
my results:

    value 1: xxx

    value 2: xxx

previous version printed:

>>> ai.Log.notice(s)
[NOTICE] - my results:
[NOTICE]   value 1: xxx
[NOTICE]   value 2: xxx

new version prints what is expected:

>>> ai.Log.notice(s)
[NOTICE] - my results:
[NOTICE]   
[NOTICE]       value 1: xxx
[NOTICE]   
[NOTICE]       value 2: xxx