[Android] Fix app will crash at exit if runtime lib not found

It's because, the code is trying to get a boolean value from
method onKepUp in runtime. It will return null if runtime lib
not found.
For other class like String, return null is OK. But for boolean,
java will try to turn Boolean object null into boolean, which
causes NullPointerException.

BUG=https://crosswalk-project.org/jira/browse/XWALK-627
[Android] Popup correct message if runtime lib is for wrong arch

For android, if the native library does not match the
cpu arch of the target device, the library file won't be
installed to the device.
So if we found that the runtime lib package exist without
libxwalkcore.so, it can be considered the runtime lib is
for another cpu architecture.
For embedded mode, the dialog will just nofity user without
the button to download from PlayStore.

TODO(wang16): If using arm Crosswalk on x86, it will work
via libhoudini, but it takes much time to do binary translation
at application startup. We should detect such case and make
Toast to users.

BUG=https://crosswalk-project.org/jira/browse/XWALK-606
Exclude gdbserver from xwalk_core_library

For the release version of cordova container, there is a license
issue to contain a gdbsever binary in the release binary. Because
the gdbserver is under GPL license.
So exclude gdbserver binary from release version and leave it
for debug version.

BUG=https://crosswalk-project.org/jira/browse/XWALK-635
Support the 2x resolution of the Tizen System Indicator

Change to inherit from ImageView instead of View as it fits our
use-case. Insert the system indicator image as a 2.0 image
representation in the ImageSkia, and use its size as the preferred
size.
Merge pull request #1283 from kenchris/SystemIndy

Support the 2x resolution of the Tizen System Indicator
Merge pull request #1275 from xingnan/gdbserver

Exclude gdbserver from xwalk_core_library
Add Halton as the owner of Android extension implementation.

Halton now is succesfully nominated as the owner of
runtime/android/java/src/org/xwalk/runtime/extension/api.
Merge pull request #1251 from wang16/abi_exception

[Android] Popup correct message if runtime lib is for wrong arch
Merge pull request #1273 from yongsheng/addhalton

Add Halton as the owner of Android extension implementaion.
[Android][SysApps] Change event names according recent spec changes.

Refer to https://github.com/sysapps/device-capabilities/issues/14, the event
names changed as below:
    attribute EventHandler  onstorageattach;     // was onattach
    attribute EventHandler  onstoragedetach;     // was ondetach
    attribute EventHandler  ondisplayconnect;    // was onconnect
    attribute EventHandler  ondisplaydisconnect; // was ondisconnect

At the same time, fixed a bug to allow pass null as callback of "onEventName".
Merge pull request #1277 from itlodge/fix_listener_logic

[Android][SysApps] Change event names according recent spec changes.
[Android] Reduce the time consumption for make_apk test (2).

Fake an empty native library "libxwalkcore.so" in make_apk test
for embedded mode. It would greatly reduce the time consumption
caused by copying library when generating the apk in embedded mode.
Merge pull request #1250 from wang16/fix_boolean

[Android] Fix app will crash at exit if runtime lib not found
Merge pull request #1279 from junmin-zhu/fakeso

[Android] Reduce the time consumption for make_apk test (2).
Implement the public user agent methods in runtime.

  The user agent is not supported in crosswalk runtime. This is
to implement the public user agent methods for crosswalk, it adds
the corresponding user agent description according to the specific
platform type.

  Base on the ZTE975 Build/JDQ39, the user agent string is listed as follows:
Mozilla/5.0 (Linux; Android 4.2.2; ZTE 975 Build/JDQ39) AppleWebKit/537.36
(KHTML, like Gecko) Chrome/32.0.1700.14 Mobile Crosswalk/3.32.49.0
Mobile Safari/537.36

BUG=https://crosswalk-project.org/jira/browse/XWALK-595
[Android] Refine the scripts for generating app packaging tool.

Currently there are lots of issues to generate app packaging tool:
1. Lots of unneeded class files are copied.
2. Two .dex.jar files are not needed by app packaging tool.
3. Some internal Java files like NativeLibraries are compiled when
packaging web apps. They should be handled internally inside of
xwalk runtime.
4. Refine the code for generating app packaging tool.
5. Invalid the python file mode.
6. Merge two jars for runtime activity and runtime client.
Fix all above issues with the changes for gyp generation and the
generation python tool.

BUG=https://crosswalk-project.org/jira/browse/XWALK-608
[Runtime] Add application main document manifest handler

With this manifest handler we can access the application main document related
info directly from MainDocumentInfo instead of parsing the manifest manually.
An unit test for the handler is also added.
[Runtime] Basic application onLaunched event support

In order to follow the main document lifecycle events, we need to launch the
application through "onLaunched" event.

Different from Chrome onLaunch event
(http://developer.chrome.com/apps/app_runtime.html#event-onLaunched), we will
only support xwalk.app.runtime.onLaunched(function callback) without launchData
object. The callback will be called without any parameter when the application
is launched explicitly (from home screen launcher or from command line).
[Runtime] Add application onLauched event browser test
Merge pull request #1233 from seanlong/event_router

[Runtime] Application main document manifest handler and onLaunched event support