fix TiddlySpace beta target creation

use tiddlywiki_externaljs_tiddlyspace_beta.html.recipe instead of alpha
recipe (so links on TiddlySpace point to "beta_*" files
add external targets to main build script

create/copy external JS and HTML target files:
tiddlywiki_externaljs.html
tiddlywiki_externaljs_tiddlyspace.html
twcore.js
jquery.js
jquery.twstylesheet.js
fixup copy for TiddlyWiki.html beta target

copy index.html to TiddlyWiki.html (for use by TiddlySpace???)
Merge pull request #18 from ericshulman/master

added external JS build targets to main build script