nits to the pubspec and treeview
Add package-files-are-editable dev flag

This is to facilitate debugging of package-related issues.

One thing that doesn't work currently: if a package file is open while the flag is off, and then the flag is turned on and CDE is restarted, the reloaded source is still read-only. It needs to be closed and reopened to make it writable.
Merge pull request #3316 from devoncarew/devoncarew_pubspec_nits

nits to the pubspec and treeview
Remove no longer used flags + reorganize light Ace themes a bit
Fix ordering of items in the CSS
Merge pull request #3318 from ussuri/minor-cleanups

Fix ordering of items in the CSS
remove the test runner code from ide/; move to using the chrome_testing package
add a pub artifiact to the gitignore file
Merge pull request #3322 from devoncarew/devoncarew_pub_files

add a pub artifiact to the gitignore file
Address comments + remove 2 bad themes
Merge pull request #3319 from ussuri/clean-up-some-flags

Remove no longer used flags + reorganize light Ace themes a bit
Merge remote-tracking branch 'upstream/master' into add-flag-to-edit-package-sources

Conflicts:
	ide/app/lib/spark_flags.dart
Add a default for new flag to app.json
Merge pull request #3321 from devoncarew/devoncarew_use_test_package

remove the test runner code from ide/; move to using the chrome_testing ...
bind ket events to commands
adding a sample native messaging example
update README
fix nit
Merge pull request #3327 from devoncarew/devoncarew_key_events

bind key events to commands
address comments