Preparing the project for GYP

GYP expects the code has a folder "src" as the base dir.
Deleted the Visual Studio solution/projects as well as
the Linux Makefile. They will be created according to the
GYP files automatically.
Put empty GYP files in place to start with.
Created a basic GYP file for the 3 build targets

Had to clean up the gtest dir, so the gtest header can be included
as expected. There was also a problem with the naming of "time.h"
within the engine source dir. The engine_test target will not build
with this file in the include path. Renamed it to "mytime.h" till
we have a better name for that.

At the moment only default parameters are set within the generated
make files. The targets engine and engine_test get build and all
unit tests pass.

The next step is to get it build on Windows.
Added GYP build support for Visual Studio

It is now possible to generate the Visual Studio solution
files on Windows and to build on Windows and Linux the
Debug and Release builds for x86.

Next steps are to support also x64 builds on Windows and
Linux.
Reworked the GYP configuration

This time I took the chromium common.gyp as example.
It is much better organised than what I had before
and defines now also 64 bit builds on windows.
Fixed tge GYP config vor Visual Studio

The config contained some mistakes, I think I need some syntax
highlighting of the GYP keywords in VIM.