Add Documentation in CHANGELOG.md for CFL #371

- related to the pre-release question in #378
Merge pull request #379 from ax3l/doc-cflUnitless

Add Documentation in CHANGELOG.md for CFL #371
fix linker failer

if PMACC_VERBOSE=16777215 (HEX: 0xFFFFFF) than we get a linker error

```
src/libPMacc/include/debug/VerboseLog.hpp:106:
  undefined reference to
        std::basic_string<char, std::char_traits<char>, std::allocator<char> >
        PMacc::getLogName<PMacc::LogLvl<17ul, PMacc::PMaccVerbose> >
        (PMacc::LogLvl<17ul, PMacc::PMaccVerbose> const&)
```