add an option `--single-env` to tracd for serving a single project without the project listing (fixes #3506)
add an option `--single-env` to tracd for serving a single project without the project listing (fixes #3506)

git-svn-id: eda3d06fcef731589ace1b284159cead3416df9b@3733 af82e41b-90c4-0310-8c96-b1721e28e2e2

jun66j5/trac-ja,jun66j5/trac-ja,walty8/trac,walty8/trac,jun66j5/trac-ja,jun66j5/trac-ja,walty8/trac,netjunki/trac-Pygit2,netjunki/trac-Pygit2,walty8/trac,netjunki/trac-Pygit2