Make docgen able to generate pkg docs and save the package names

Make docgen able to generate pkg docs and save the package names

R=terry@google.com

Committed: https://code.google.com/p/dart/source/detail?r=29387

[Alan Knight, 2013-10-22 18:42:49]

This adds a property packageName to the generated Library object and find the
package name from the pubspec to put in it for libraries that come from file
URIs. It also filters out those libraries that aren't directly in the lib
directory. And it switches the default format from the scripts to be JSON, adds
a script for just generating the docs for everything in a local directory, and
removes a lot of trailing whitespace because I hadn't touched those files
before.

[terry, 2013-10-24 14:17:30]

LGTM just one minor suggestion.

https://chromiumcodereview.appspot.com/35743002/diff/40001/pkg/docgen/lib/doc...
File pkg/docgen/lib/docgen.dart (right):

https://chromiumcodereview.appspot.com/35743002/diff/40001/pkg/docgen/lib/doc...
pkg/docgen/lib/docgen.dart:335: filteredEntities.map((e) => e.typeName));
Minor point, I'm sure it's not a perf issue now, but one visit thru the map is
probably more efficient then iterating twice once for keys and once for values.

var index = {}'
filteredEntities.map((e) => index[e.qualifiedName] = e.typeName;)

[Alan Knight, 2013-10-28 20:12:43]

Committed patchset #2 manually as r29387 (presubmit successful).