Fix pattern

Fixing RFC_2617_PARAM to be able to parse timestamp with a , separated decimal part (for example, for french people)

Fix Signature.toString()

I don't understand why created and expires disappeared from Signature string if algo is not HS2019.
What I propose is to only add those informations if not null and if headers contains (created) or (expires)

Add a new Signer.sign() method

Create a new public Signature sign(final String method, final String uri, final Map<String, String> headers, Long created, Long expires) throws IOException

The idea here is to provide a way to sign giving the choice of created and expires timestamp.
It is useful for a validation case from a string, you are able to regenerate a signature from input and keep control on those two timestamps.