[0.4.13][RAPPS] Pick some simplifications from master up to 0.4.15-dev-3726-gc262020...

[0.4.13][RAPPS] Pick some simplifications from master up to 0.4.15-dev-3726-gc262020 (e.g. CORE-18018 and (#2751))

As the dialog simply displays the copyright names and nothing particular it makes sense to use ShellAboutW() instead.

Several fixes ported back:
0.4.15-dev-3726-g c262020016f637c8a158a43db443e0ebc071d2f8 README CORE-18018
0.4.15-dev-3724-g 3a7c0d82d2fd4f1413cf0ed50eedad52b107d491 size fallback part 1 CORE-18018
0.4.15-dev-3569-g b5a6357d932ea6cc4e3198bb4ad1956b6a235f0c available.h/.cpp Strip 3 useless functions
0.4.15-dev-384-g 393a2c42fec59341271a53d4f87c253a13aabf9c CDPath in README
0.4.15-dev-227-g a6084d7440c260eb0ecb352f3b20f8c3a89162a2 ShellAbout() (#2751)
and some whitespace corrections, especially in cabinet.cpp