Remove references to nonexistent include directories

Some of these were legacy references to absolute paths outside of
the project itself.
Don't use the encoder include dir when building the decoder
Unify the include dirs within the decConsole project

Some include directories were only present in debug builds.
Unify the include directories in the WelsVP project

Some directories had a trailing slash in some configurations, but
not in other configurations. Make sure the directories are the same
in all configurations.
Remove unnecessary, empty, file specific FileConfiguration blocks in vcproj files
Don't hardcode SuppressStartupBanner=true, this is the default value

The fewer fields overridden, the better.
Merge pull request #813 from mstorsjo/msvc-proj-cleanup

Clean up the MSVC project files