fix vcxproj generation for CONFIG-=flat

Commit 4f21eb03 broke the generation of non-flat vcxprojs.
XTreeNode passes filter names to outputFileConfigs that have
the source subdirectory suffixed (e.g. "Generated Files\subdir").
That's why the original code tested the filter names with
QString::startsWith.
I've changed the signature of outputFileConfigs to take a filterId
parameter which contains the unaltered filter name (e.g.
"Generated Files") that will determine the correct filter.

Task-number: QTBUG-41746
Change-Id: If33428526a098f433cd6ceb8ab6608bd9f94ef17
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
fix VS 2008 project file generation

Commit 4f21eb03 utterly broke the project file generation for
VS 2008. The introduced filterByName convenience methods looks for
filter names like "Generated Files", but the code path for
VS <= 2008 used filter names like "GeneratedFiles".
The generated projects were valid but empty.
This commit ensures that both VS generators use the same filter
names.

Task-number: QTBUG-41821
Change-Id: I828fa911bae8d835b073a4c2260316127cc72cda
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>