io.cljs: implement classpath-like search for resources.

cljs.io/*clojurescript-home* is set to the top of the Clojurescript
directory.

cljs.io/*classpath-suffixes* represents the list of subdirectories
with *clojurescript-home* that are searched for resources.
factor out jqconsole code into webconsole.cljs
File editor for web repl:
1. Create a CodeMirror-based file editor (in webedit.cljs)
2. Create webrepl3.cljs and repl3.html, which use the file editor
3. build2.sh builds the console-only version of clojurescript.net;
   build3.sh builds the version including both console and file editor.

The file editor's contents can be evaluated in the REPL by pressing
Ctrl/Cmd+E, and the editor itself can be shown and hidden by pressing
the Show/Hide file editor link.
Merge remote branch 'arthuredelstein/web-edit' into cljs_in_cljs