Cleanups, especially get rid of "usage namespace ..."

"usage namespace" is in most coding standards not seen as good practice.
Especially when same classes are used in different namespaces, the
behavior is unpredictable. It also brings more clarity if
e.g. "std::string" is used instead of "string" only.

Also cleaned up many comments that doesn't help. Including names of
developers who contributed this code and large chunks of uncommented code.
Both can be seen and retrieved vom the version control system (Git) anyway.

"#pragma once" is nowaydays supported in all compilers (gcc, vc). So no
need for include guards. It also seems to improve compilation speed.

There are still some issues left I've found:
* FlexRayDatabaseDissociateDlg.cpp: contains "sizeof(std::string)"
* XMLUtils.h: switch has duplicated case SW_SHOWMAXIMIZED=SW_MAXIMIZE=3

Signed-off-by: Tobias Lorenz <tobias.lorenz@etas.com>