While the recent commit 7e5745f solved the issue of having an
independent blob-stamp file, which was possible to become out of
sync with the necessary web/blob/files.go file, this change further
simplifies the setup by merging the two Makefile.
The only purpose of web/Makefile was to call targets in
web/blob/Makefile. As all dependencies for blob/files.go are
outside of the blob/ directory, the separation isn't logically
necessary.