Closes #1097 so zcash-cli now displays license info like zcashd.

LicenseInfo is refactored from init.cpp to util.cpp so that the
bitcoin-cli makefile target does not need to be modified.

src/util.h

@@ -135,6 +135,9 @@ boost::filesystem::path GetTempPath();
 void ShrinkDebugFile();
 void runCommand(std::string strCommand);
 
+/** Returns licensing information (for -version) */
+std::string LicenseInfo();
+
 inline bool IsSwitchChar(char c)
 {
 #ifdef WIN32