Refactor of otbWrapperApplication.h

Summary

The purpose of this MR is to remove implementation code from the header file otbWrapperApplication.h:

• Move implementation of simple methods to the cxx
• Replace itkSetStringMacro and itkGetStringMacro with simple methods with the same type signature
• Move otbGetParameterImageMacro to the cxx
• Fix duplicated implementation of Application::GetParameterImage (previously in !143 (closed))

Rationale

Reduce OTB build time, see #1649 (closed).

Implementation Details

Classes and files

M       Modules/Wrappers/ApplicationEngine/include/otbWrapperApplication.h
M       Modules/Wrappers/ApplicationEngine/src/otbWrapperApplication.cxx

Tests

Does not affect tests.

Documentation

NA

Additional notes

itkSetStringMacro actually defines two methods: virtual void Set##name (const char *_arg) and virtual void Set##name (const std::string & _arg). I have only added the string version. Do we need to also keep the const char* version?

Copyright

The copyright owner is CNES and has signed the ORFEO ToolBox Contributor License Agreement.

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***Check before merging:*** - All discussions are resolved - At least 2 votes from core developers, no vote. - The feature branch is (reasonably) up-to-date with the base branch - Dashboard is green - Copyright owner has signed the ORFEO ToolBox Contributor License Agreement