use constant fmt string when printing error in OTPseudonym
disable check -Wformat-nonliteral

This is only workaround. Creating bug for this.
Merge pull request #341 from mhamrle/error_fmt

use constant fmt string when printing error in OTPseudonym
CMake: enable format warnings also for clang
Merge pull request #343 from toxeus/formatClang

CMake: enable format warnings also for clang
Removed unused case OTClient::issueAssetType.
Removed unused case OTClient::sendUserMessage.
Removed unused case OTClient::checkUser.
Merge pull request #334 from benma/ProcessUserCommand

Start removing dead code from OTClient::ProcessUserCommand.