CMake config fix.
Merge pull request #134 from BSMaidSafe/MAID-131_DisableLevelDBTests

CMake config fix.
CMake-2.8.12 configuration fix.
Merge pull request #136 from BSMaidSafe/MAID-133_PolicyCMP0026

CMake-2.8.12 configuration fix.
Issue a developer warning if duplicate files are passed into CMake functions 'ms_add_executable' or 'ms_add_static_library'.
Merge pull request #141 from Fraser999/duplicate_file_warning

Issue a developer warning if duplicate files are passed into CMake funct...