Make includes consistent: Google C++ style guide, no "../", etc.
cppcheck: update include folder.
clangformat on OTSignature.hpp.
Merge pull request #293 from benma/cleanup

Made all includes consistent
Removed OTPseudonym::CertfileExists.
Removed OTClient::ConnectToTheFirstServerOnList.
Removed OTString::ConvertToLowerCase.
Removed OTIdentifier::CopyTo.
Removed OTCrypto::DeriveKey and cleaned up comments.
Removed OTEnvelope::(Get|Set)AsBookendedString.
Removed OTSocket::GetBindingPath, GetConnectPath.
Removed OTContract::GetContractPublicKey, GetFoldername..
Removed unused functions in OTPseudonym.
Removed OTLog::PushMemlogBack, OTLogStream::overflow.
Removed OTSymmetricKey::ReGenerateHashCheck.
Removed OTServerConnection::SignAndSend.
Merge pull request #300 from benma/unusedFuncs

Unused funcs
OTContract: Remove deprecated tag "key"
OTPseudonym: Remove deprecated code (old key system)