[Android] Add "xwalk" prefix to manifest extensions

According to http://w3c.github.io/manifest/, vendor
extensions should have vendor prefix.
For Crosswalk on Android, launch screen is an extension
of manifest.
This commit add "xwalk" prefix to all related paths.
The legacy paths are still supported, but will print a
warning message to logcat.

Related to XWALK-1918
Application storage should not cache all installed applications data

Since we dropped "Main document" functionality there is no need for
Application storage to cache all installed applications data, besides
doing so uselessly wastes memory.
Another goal of this patch is preparation Application storage for accessing
it from other processes than browser process (e.g. from xwalkctl process)
and for using different Application storage implementations.
Merge pull request #2119 from pozdnyakov/Refactor_ApplicationStorage

Application storage should not cache all installed applications data
Bump version to 8.36.159.0
Merge pull request #2116 from wang16/w3c_manifest

[Android] Add "xwalk" prefix to manifest extensions
DEPS.xwalk: Roll chromium-crosswalk (6488cb7->f8b103e)

f8b103e Merge pull request #172 from xingnan/1833
dcf89f9 [Android] Fix the crash of GetUserMedia
Merge pull request #2123 from xingnan/1833

DEPS.xwalk: Roll chromium-crosswalk (6488cb7->f8b103e)
[Extensions] Pass the runtime_variable ownership forward

We can avoid a few copies if we use the shared_ptr + .Pass() idiom.
[Extensions]: Expose the extension path to the extension

There is an use case, specially with pycrosswalk, where you can have
multiple instances of the same extension loaded using symbolic links.

The extension needs to know about itself (the path to be more precise)
to figure out what python script it should load.