[Tizen][Runtime] Change to initialize access whitelist when webkit has been initialized.

After rebase to M37, in some conditions, there's no need to create javascript
context, so it's not a right place to init the access white list. This patch
will change to do it after webkit engine initialized.

BUG=XWALK-2295
[Android] Enable reflection layer generator

Add a python script to generating code for classes in
org.xwalk.core from classes in org.xwalk.core.internal
which need to be exposed in Embedding API.

For each class of org.xwalk.core.internal which needs to be
exposed in Embedding API.
A bridge class and a wrapper class will be created for it.
The bridge class is a subclass of internal class and maintains
a wrapper object of this type.
A wrapper class is in org.xwalk.core and be exposed in Embedding
API, it maintains an instance of bridge object as well.
Wrapper and bridge talks to each other via pure reflection. So
they don't have to be in the same package in future.

TODO: JavascriptInterface class needs to be placed in wrapper and
pass the class object to internal for recognition of javascript
interface.

BUG Related: https://crosswalk-project.org/jira/browse/XWALK-1638
Merge pull request #2251 from wang16/reflection_layer

[Android] Use script to generate core code which is a simple wrap of core internal
Merge pull request #2299 from takethathe/allow-navigation

[Tizen][Runtime] Change to initialize access whitelist when webkit has been initialized.
Do not use scripting inside gclient

After recent changes on depot_tools, using "for loops" inside gclient
config file apparently is not possible anymore. Also, the "solutions"
now has to be explicitly declared.

BUG=XWALK-2379
Merge pull request #2342 from tmpsantos/gclient_fix

Do not use scripting inside gclient
Bump version to 9.37.195.0
[Android] Packaging enhancement for external extensions

Add extension_manager.py to download online extension repo.
Usage:
extension_manager.py
--add=https://github.com/shawngao5/crosswalk-android-extensions.git
--name=iap --project=/home/xgao/tmp/iap/
Downloaded extensions are saved under <project>/extensions/

This tool also can remove, list and search local extensions.

To package these extensions into app, you don't have to provide full path.
Developer just need provide the name of extension, such as "iap", to the
--extension option of make_apk.py.

BUG=XWALK-1947