added mobile network for response

Merge pull request #17 from verifykit/feature/base-url-set

feat(feature/base-url-set): Base url can be changed externally so that services using the SDK can mock while writing tests

 wrong variable type fixed

 added length parameter for otp send response.

 added preg match for session id

 deleted unused use line.

 some textual edits

 websdk document updated.

Merge branch 'otp-methods' of https://github.com/verifykit/verifykit-…

…sdk-php

 restapi error codes edited after cr.