Remove strings & command-line-parser submodules.

These are now part of base Open Dylan.
Bump concurrency submodule to current version.
Bump uri submodule to current version.
Merge pull request #41 from dylan-lang/submodule-cleanup

Submodule cleanup
Switch to https URLs instead of git URLs.

This eases things for people behind a proxy.
A few cleanups and comments for http-client.
Merge pull request #42 from cgay/simplify-client

A few cleanups and comments for http-client.
[code-browser] Don't depend on graphviz-renderer for now.

The code involved wasn't actually in use.
[code-browser] Need to use http-server.
[code-browser] Update for find-registries API change.
[code-browser] Add registry entry.
[code-browser] Remove usages of url-map, use resources.
[code-browser] Use regular resources for entry points.
[code-browser] Allow a slash at the end of a library or  module, so the next part will be empty.
[code-browser] Set content type.
[dsp] Fix parse-tag-prefix for when near EOF.
Merge pull request #43 from dylan-lang/fix-parse-tag-prefix

[dsp] Fix parse-tag-prefix for when near EOF.
[code-browser] Don't fail when source can't be found.
[code-browser] Fix whitespace @ EOL.
[code-browser] Add a simple index page.