use full 'hive::log::*' references instead of short 'log::*'

simple 'log::' expression confuses some old gcc compilers, in that case 'log' is ambiguous because of log() function from math.h

there are three different workarounds:
 - use full classified names like 'hive::log::Logger a;'
 - use 'using namespace hive::log; Logger a;'
 - use 'namespace L = hive::log; L::Logger a;'