[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][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.
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).
[Android] Add arch option for packaging tool in embedded mode.

Accept the arch option from developer for embedded mode. if the arch
option is unspecified, all available platform apks will be generated.

Usage: python make_apk.py --arch=x86 ...

BUG=https://crosswalk-project.org/jira/browse/XWALK-598