Global attribute name standardization for widgets
Better attribute names + other cleanups in widgets
#325

- 1), 2) should be fixed with this update
- 3) should be defined what should happen

Open question:

- I don't know if large and small should be exclusive or.
I guess so, but it was not.

Note:

- I tried to minimize updates to the btnClasses map but that didn't work
I filed a but, see code comment on method `updateBtnClassesJob()`

#786

- I think the button tests is thoroughly.
It can be refined of course if issues occur
or if someone has ideas what can be additionally tested

Note:

- drone.io doesn't install content_shell by default
this has to be done manually (I haven't done it myself yet)
if you add `test/run.sh` to the build script for drone.io the test will probably fail
Scroll center item into position
Merge branch 'umop-outline-remember_position' into umop-outline-sync_scroll
Merge branch 'master' of https://github.com/dart-lang/spark into umop-outline-sync_scroll
Fixed scrolling to include as many rows as possible
left and right border experiment.
reverting experiment
Merge branch 'master' of https://github.com/dart-lang/spark into umop-outline-sync_scroll
initial WIP library
nits
Fixed NPE and timing issue
add js linting
nits
cleanups
Optimize git checkout.
Merge branch 'master' of https://github.com/dart-lang/spark into umop-outline-sync_scroll
Merge remote-tracking branch 'upstream/master' into merge-spark-button-changes

Conflicts:
	widgets/lib/spark_button/spark_button.dart
	widgets/lib/spark_button/spark_button.html
	widgets/pubspec.yaml
Upgrade spark-button test to new Polymer and new spark-button