add example for spark-button
add pub get back to spark
fix nits
added getter for pub manager
moved completion message display to spark
removed message
Improve usability of cannot-launch alert.

The previous language didn't indicate which way the flag should be
set, but merely said to "check" it. The new language is more
precise. The alert now presents a link that can be manually copied
and pasted into an address bar, taking the user directly to the
relevant flag.

TBR @sergeygs
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review feedback
Merge pull request #1258 from keertip/pub

add pub get back to spark
add TODO comment about spark-button
Merge pull request #1257 from sunglim/button_example

add more examples to spark-button
merge upstream/master
Merge pull request #1265 from devoncarew/master

compressed sample's images
Merge pull request #1264 from sunglim/properties-dlg

show properties for all files
re-size the cannot launch dialog