fix bugs for Ubuntu cmake not find Qt5 and bitshares

My OS is Ubuntu 12.04.3
1.fix this error:
By not providing "FindQt5Core.cmake" in CMAKE_MODULE_PATH this project has
  asked CMake to find a package configuration file provided by "Qt5Core", but
  CMake did not find one.

2.fix CMake Error at CMakeLists.txt:82 (add_subdirectory):
  add_subdirectory given source "bitshares" which is not an existing
  directory.