Assets controller fixes

* Replace usages of Play.current with Play.maybeApplication. This
  ensures that at very least templates using assets reverse routes can
  be rendered without a running application.
* Used Option instead of exceptions to handle NotFound
* Fixed resource leak in digest cache
* Use Global bad request handling
* Let Play handle errors
[DOC] Fix jpa config example
Merge pull request #3125 from cedricziel/jpaDocFix

[DOC] Fix jpa config example
Document form mappings for other date types
Merge pull request #3126 from richdougherty/date-docs

Document form mappings for other date types
modify version number

0.1.3 --> 0.1.4
Merge pull request #3128 from diceit/ide-ensime-014

modify version number for ensime in doc
Merge pull request #3122 from jroper/assets-no-play-current

Don't use Play.current anywhere in Assets
Add missing lang attributes for improved accessibility (see http://www.w3.org/TR/UNDERSTANDING-WCAG20/meaning-doc-lang-id.html and http://www.w3.org/TR/WCAG20-TECHS/H57.html).
Merge pull request #3139 from danielnixon/master

Add missing lang attributes for improved accessibility
fix javadoc indent
Merge pull request #3142 from gmethvin/json

fix javadoc indent
Simplify json response example and add an example of serializing a Java object
Merge pull request #3144 from benmccann/json-docs

Simplify json response example and add an example of serializing a Java object
Refactor server code in preparation for akka-http backend

Moved the main method out of NettyServer and into a new class
called ServerStart. Refactored the existing server start logic
so it is easier to understand. Added tests for server start
logic.

Consolidated server configuration into a single class,
ServerConfig. This configuration class will be used by both
the Netty and akka-http server backends.

Created an abstraction for a VM process so that server
creation can be tested properly. This trait, ServerProcess,
provides alternative methods to call instead of calling
System.getProperties, System.exit, etc.

Made it possible to start servers other than NettyServer,
by providing a system property called "server.provider"
that locates a... ServerProvider. The ServerProvider class
creates the actual server. This feaure is only exercised
in unit tests for now.

Also split out some of the smaller classes that were
previously in NettyServer.scala into other files.
Add parentheses to stop compiler warnings