new tool to generate new projects etc.

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Cmd: @obazl//new -- -p <projname> plus whatever other params.

Should generate:

• .bazelignore
• .bazelrc
• .gitignore
• ./private/.gitignore, ./private/bazelrc
• .bazelversion?
• .obazl.d/opam/local/BOOTSTRAP.bzl
• BUILD.bazel
• BUILD.bzl (dummy, for demo)
• COSWITCH.bzl
• WORKSPACE.bazel
• WORKSPACE.bzl (with demo fetch/bootstrap function)
• bzl/hosts/BUILD.bazel
• src/BUILD.bazel and some source files to build
• test/BUILD.bazel with some test targets

Maybe:

• bin/
• tools/ with some scripts like wss

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@obazl//new:ws is done but needs portability improvements.