With the old policy the most recent log would not be printed until the next
log is produced (which may be indefinitely). This change prints logs
immediately along with a time delta since the previous log.
* General improvoments to the loader app:
* Show a message after 8 seconds if no connection comes in.
* Show a progress bar as files are being uploaded.
* Hide the spinner just before launching the application.
* General improvements to the "flutter run" UI:
* Add "?" key as a silent alias for "h".
* Make the help text bold so it doesn't get mixed with the logs.
* Make "R" do a cold restart when hot reload is enabled.
* Supporting features and bug fixes:
* Add support for string service extensions.
* Other bug fixes:
* Expose debugDumpRenderTree() outside debug mode.
* Logger.supportsColor was missing a getter.
* Mention in the usage docs that --hot requires --resident.
* Trivial style fixes.
Also, make it clear the screen between results so it's more obvious
what's going on when you have new results (especially when you have
fixed everything).
* refactor the --resident run option into a separate file
* update daemon to run --resident apps
* re-plumbing daemon start
* send app logs
* update tests
* review changes
* fix test runner
* remove PackageMap.createGlobalInstance; rely on the ctor
* review comments
* more terse flutter upgrade
* fix an issue when updating and the engine update code has changed
* call flutter precache; add a --no-color hidden option
* fix a lint related to getters/setters
