Finalize CPPLINT

[FelixS90]

Is your feature request related to a problem? Please describe.
With the completion of #32 we still have some cpplint issues left to fix (or permanently accept) that are currently filtered out in CPPLINT.cfg.

Describe the solution you'd like
Apply some of the fixes primarily applied to Src/libCZI as part of #32 to other parts of the code like:

• Src/CZICmd
• Src/JxrDecode
• Src/libCZI_UnitTests

Src/libCZI largely passed cpplint by applying the following filter:

Any cpplint issues that are not going to be fixed (either because of feasibility or meaningfulness) should stay in the global CPPLINT.cfg. I strongly advise not to:

• introduce nested config files or
• exclude certain subdirectories from scanning

Additional context