Support generation of shared libraries in Windows

[traversaro]

Additional related modifications:

• Cleanup of visibility macros (we just use default visibility on *nix and CMAKE_EXPORT_ALL_SYMBOLS in Windows)
• Add possibility of selecting if the library is build as shared or static using BUILD_SHARED_LIBS

[traversaro]

AppVeyor builds are failing for the following reason:

• [[noreturn]] does not work on VS2013
• Tests are not working on all other builds

[traversaro]

The two problems were the usual problem of dll not found by test in Windows (see https://github.com/robotology/how-to-export-cpp-library/issues/4 for a more in-depth discussion) and the fact that I removed the __declspec(dllexport) even from the MODULE that is meant to be loaded at runtime. CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS remove the need of exporting symbols in library linked at link time, but dllexport is still need for dll loaded at runtime .

[coveralls]

Coverage remained the same at 60.263% when pulling 25fbf265ec27504c89d172ddadb7407e6393ce1f on traversaro:windowsShared into 540ffafb474fd0fdcfd08b51629353aba919950c on robotology:devel.

[coveralls]

Coverage remained the same at 60.263% when pulling 25fbf265ec27504c89d172ddadb7407e6393ce1f on traversaro:windowsShared into 540ffafb474fd0fdcfd08b51629353aba919950c on robotology:devel.

[aerydna]

@traversaro if you resolve the conflicts we can merge it.. btw we have to think a method to add feature notes to the changelog file without everyone operating directly on it. something like this @Nicogene @drdanz https://github.com/masukomi/changelog_manager

[aerydna]

merged, thanks!