Merge tag 'v1.0.26' into develop

Release of v1.0.26 - support for Message Inbox; some refactorings in the source code
[#refactor] - eliminated most of the code duplication in LPClient.php
[#121] - added support for registering customers
[#versionBump] - v1.0.27
Merge branch 'release/1.0.27'