Simplify the constructor for Sinequa class

[NISH1001]

Description

Currently pynequa.core.Sinequa class can only be initialized from a config dict. I propose moving the config-based construction to a new classmethod and use barebone parameters as a primary constructor

class Sinequa(API):
    def __init__(self, app_name=<default?>, query_name=<default?>, ..., debug: bool = False):
        pass

    @classmethod
    def from_config(cls, cfg: dict) -> Sinequa:
        pass

Why

Because we want more nuanced control of the construction without having to know what goes in the config. Normally config-based classes are initialized through secondary constructor