Add option for reuse curl handle

[yann01240]

It improves performance in multiple queries to avoid SSL handshake at each request.

[stokito]

The whole design of the lib looks for me as a one-time call usage. It doesn't use OOP and stores almost all request configs to a class static variable. This makes managing of state difficult.
As for me, it might be too dangerous to reuse an old curl handler instead of the creation of another one with clear settings.

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