[Android] Put app resource in sub directory of assets

Before this all app resources are put in assets, which may cause
confliction with other resources(of runtime, extensions etc).
So we define a sub directory "www" to put the app resources
instead.

BUG=https://crosswalk-project.org/jira/browse/XWALK-174
[Android] Add app URI scheme support

1 App URI scheme is part of sysapps API, http://app-uri.sysapps.org
2 On Android the local resources are located in assets, which could
be accessed by file:///android_asset/ scheme. So we bridge the app
URI to file URI.
3 Add the HTTP response support(200, 400, 403, 404, 501).

BUG=https://crosswalk-project.org/jira/browse/XWALK-174
[Runtime] Register system events information into database during installation.

As is mentioned in https://crosswalk-project.org/jira/browse/XWALK-519,
this PR registers system events at application install time. In detail,
after installation of application pacakge is completed, the main
document will be executed to register the events into system database.
Merge pull request #1255 from xingnan/app-shcheme

App scheme
Merge pull request #1309 from ShDavidliu/io_thread_client

[Android] Enable the io thread client in xwalk content.
[SysApps][Android] W3C SysApps Messaging API

The implementation is based on 29 November 2013 editor's draft version
http://www.w3.org/2012/sysapps/messaging/

Completed features list:

Send/receive SMS messages.
Find/list SMS messages
Find/list SMS conversations
Delete SMS messages
Delete SMS conversations
Mark SMS message read status
Mark SMS conversation read status
Feature: https://crosswalk-project.org/jira/browse/XWALK-53

MMS Features is holded. Waiting for Android official Mms API ready.
Merge pull request #1339 from shawngao5/shawn_dev_sms

[SysApps][Android] W3C SysApps Messaging API
Bump Crosswalk's major version to 4.

BUG=https://crosswalk-project.org/jira/browse/XWALK-712
Merge pull request #1362 from rakuco/crosswalk-v4-bump

Bump Crosswalk's major version to 4.
[SysApps] Introduce the SysAppsManager

This class will be the single entry point for registering all
the SysApps extensions. It should be the only class of the "sysapps"
namespace exposed to other subsystems.

In the future it will also manage the lifecycle of data providers (platform
abstractions for extensions like DeviceCapabilities).
[SysApps] Add a "sysapps" master flag

A single flag to disable all the SysApps APIs.
[SysApps] Add unit tests for the SysAppsManager
[Extensions] Fix runtime symbol missing for xesh

Fixes runtime error when building with component=shared_library.

symbol lookup error: libglue_child.so: undefined symbol: HeapProfilerStart
Merge pull request #1364 from tmpsantos/xesh_missing_symbol

[Extensions] Fix runtime symbol missing for xesh
Merge pull request #1235 from shaochangbin/register-system-events

[Runtime] Register system events information into database during installation.
Merge pull request #1357 from tmpsantos/sysapps_manager

[SysApps] Introduce the SysappsManager
[Runtime] Move application runtime& event extension under xwalk::application namespace.

Present ApplicationEventExtension & ApplicationRuntimeExtension are
located inside namespace "xwalk". Actually they are parts of
"application module". This PR moves the two inside namespace
"xwalk::application".
Implement DOM screen.lockOrientation and screen.unlockOrientation

Can be tested manually with http://jsbin.com/IJapIVE/4
Merge pull request #1365 from shaochangbin/app-extension-namespace

[Runtime] Move application runtime& event extension under xwalk::application namespace.
Merge pull request #1367 from kenchris/lockOrientation

Implement DOM screen.lockOrientation and screen.unlockOrientation