change from Claim_escrow_earnings -> Sign_Release function

[techrebelgit]

The claim_escrow_earnings function was from previous focus on freelancers.
We added release_signer address because there are usecases weere the funds release will not happen as a claim by the service provider, but as a release signature either by the platform or even the client.
So we we need to modify so that the auth is to the release_signer address and no to the service_provider one.

Basically the release signer is who can release funds TOWARDs the service provider.

[armandocodecr]

The corresponding changes have already been added for what was requested in this issue.