[Application] Add current application exit/hide support

The supported APIs are listed below:
Application.hide/exit

The implementation leverages running application object exported by the runtime
process on the DBus session. The "Terminate" and "Exit" methods of it only
permit the launcher process to access.

Supplement Application example for new added APIs are also added.
Bump version to 0.50
[Tizen] Don't throw exception when empty files are read

This patch removes check that throws exception when empty file is read.
Bump version to 0.51
[DLNA] Add sort options for MediaServer example

This patch adds sorting options to mediaserver.html
Bump version to 0.52
[Content] Update instance counter in anycase

Update the instance counter in any case and not just when connected sucesfully
to the database. Otherwise, the assert will cause crash in dtor later on.

BUG=https://crosswalk-project.org/jira/browse/XWALK-1599
Bump version to 0.53
[Application] Add application metadata support

Below APIs are added:
ApplicationMetaData
ApplicationManager.getAppMetaData

Application metadata is specified in config.xml and can be readonly
accessed by both native and web applications.

BUG=XWALK-1610
Add OWNERS
Bump version to 0.54
[Tizen] Move MediaServer dbus objects to worker thread

This patch adds new worker thread with g_main_loop for async
dbus call processing.
[Tizen] Add support for missing virtual roots

This patch adds support for missing virtual roots:
wgt-package, wgt-private, wgt-private-tmp and ringtones.
[TEMP] Fix coding style check error

This commit can be reverted after cpplint.py updated with
CL https://codereview.chromium.org/269013009/
SysInfoDisplayWayland: Make Display adhere to our coding style.

cpplint.py was recently updated in depot_tools, and introduces a newer
style check for the indentation of items in a class declaration.
Bump version to 0.55
[Tizen] Add runtime deps needed by the Content API

In order to run Content API properly, the following packages needs to be installed

- media-data-sdk - creates the media database (/opt/usr/dbspace/.media.db)
- media-tumbnail-server - service to create tumbnails. Pulls is also media-server.
[Content] TCT crash and passrate fixes

Implement scanFile method which is heavily used by the TCT web api test suite.

Fix a crash for filter with invalid parameters (no bug yet).

Rename uri to path conversion methods more aligned with chromium.

Add test code for scanFile
Bump version to 0.56
[Speech] Fix the js api for vocalizer

BUG=XWALK-1573