Remove note about incrementalAssetsCompilation

Remove the note about using incrementalAssetsCompilation flag which no
longer exists.
Clean up Scala dependency injection, add a test for controller injection
[doc] Update documentation README to be more accurate

The README was not accurate about the packaging of documentation and how rendering of documentation was done internally.  Added some notes to about the main SBT project and the DocumentationServer.
Don't lose echo when initialising Play project settings

"play-interaction-mode" was recently introduced as a setting for Play
projects. The setting object was initialised when a Play project is
created. Unfortunately, initialising the setting object created a
JLine ConsoleReader object which, as a side-effect, disabled terminal
echo. Instead of creating a ConsoleReader at initialisation time, we
need to delay creation of the ConsoleReader until the setting object is
actually used, so echo can be restored afterwards.
Merge pull request #1476 from richdougherty/run-echo

Fix jline lost echo issues
Merge pull request #1544 from wsargent/patch-5

[doc] Update documentation README to be more accurate
Made Global handlers return futures

The results refactoring ended with Global handlers, such as onError,
onHandlerNotFound etc, returning SimpleResult, which meant they couldn't
be asynchronous.  This changes the type to Future[SimpleResult].

Also extracted code samples out of Java Global docs, and updated all
docs for this.
Merge pull request #1545 from jroper/global-handler-futures

Made Global handlers return futures
Merge pull request #1538 from wsargent/1538-change-ScalaDependencyInjection-page

[doc] Make ScalaDependencyInjection have examples, proper formatting
Merge pull request #1474 from jodyfanning/master

Remove note about incrementalAssetsCompilation
Merge remote-tracking branch: upstream/master