Added build.dart to make Polymer iterations in Dart Editor easier.

Essentially just pulls in the changes under widgets/ into ide/app/packages, allowing quick debugging of the uncompiled app.

Still needs to be run manually every time 'widgets/' change, but that can be done via the context menu or Run button of the editor without switching to command line and back.
Adjusted to the new way Polymer elements have to be defined.
Added the <spark-select> custom Polymer element (HTML's <select>)

For now derived from HtmlElement, the most generic way. An attempt to derive from SelectElement has failed so far: TBD.
Reimplement themeChooser in the Polymer UI using the new <spark-select>.

One part of reimplementation was a further refactoring of spark.dart.
Added custom context menu to Spark + do UI switching using it

Replaced the not-so-pretty links directly in the app's UI with a context menu item.

Note: there seems to be a race condition somewhere: when repeatedly switching from one UI to the other multiple timees, eventually the UI alternate windows stop opening/closing in a random fashion. 'this.window' in the code becomes null. This function is dev-only, though, and the first time switching always work,  so don't spend too much effort now figuring it out.
Equalize the height of UI elements
Removed a leftover old code
nits
Merge pull request #107 from ussuri/fix-polymer-stuff

Adjusted to the new way Polymer elements have to be defined.
Merge pull request #108 from dart-lang/cleanups

nits
review changes
Merge pull request #112 from ussuri/ui-cleanups

Equalize the height of some UI elements
Merge branch 'master' into analyzer
Addressed comments
Merge pull request #110 from ussuri/add-build-dart

Added build.dart to make Polymer iterations in Dart Editor easier.
Addressed comments
Attempt to go back to CRLF line endings to appease github's diff.
Addressed comments
Micro-improvement

...In light of recent discussion re: braces with control statements (in some pull request).
Merge pull request #111 from ussuri/context-menu-ui-switching

Context menu ui switching