Allow a custom company name in Signer 2FA SMS

When SMS auth is used for signer authentication, it will always say "AssureSign". Twilio has the capability to have different "profiles" that show a different company name in their set verification code message. We should consider allowing customers to use their Account Name.

This was given as feedback in support case 00729173, where they are concerned about customer confusion and trust. The customer said: "given the amount of spam people have to fend off, the more personalized the message can be; with details that are shared ahead of time, A: the client knows what to look for and B: there's a certain amount of authentication to the message as well."