[Android] Use activity for Presentaion extension

android.app.Presentation requires activity instance
for constructor. Use the weak references stored
in PresentationExtension.

BUG=https://crosswalk-project.org/jira/browse/XWALK-2542
[Android] Embedding API version 3.0

New APIs in 3.0:
XWalkPreferences.JAVASCRIPT_CAN_OPEN_WINDOW;
XWalkPreferences.ALLOW_UNIVERSAL_ACCESS_FROM_FILE;
XWalkPreferences.SUPPORT_MULTIPLE_WINDOWS;
XWalkPreferences.PROFILE_NAME;
XWalkPreferences.setValue(String key, int value);
XWalkPreferences.setValue(String key, String value);
XWalkPreferences.getBooleanValue(String key);
XWalkPreferences.getIntegerValue(String key);
XWalkPreferences.getStringValue(String key);

Deprecated API in 3.0:
boolean XWalkPreferences.getValue(String key);
[Android] Update xwalk_app_template after shared layer move into core

The main changes are:
1. There is no xwalk_runtime_java.jar any more.
2. Split xwalk_core_library_java.jar into app part and library part
   to support shared mode.
For aar package, since it on accepts one classes.jar, still create
xwalk_core_library_java.jar and pass it as argument when creating
aar package.

BUG=https://crosswalk-project.org/jira/browse/XWALK-2537
Merge pull request #2444 from wang16/make_apk_shared_mode

[Android] Update xwalk_app_template after shared layer move into core
Merge pull request #2441 from wang16/presentation_api

[Android] Use activity for Presentaion extension
Merge pull request #2442 from wang16/embedding_api

[Android] Embedding API version 3.0