[Application][Tizen] Move the installation steps into a new file

When running Crosswalk on Tizen in the 'run-as-service' mode we use
the new installation mode, that only a small binary will run as root.
[Packaging] Set the install helper tool as 'set-user-ID-root'

This will allow this tool to finish the last pieces of the installation
of an application: copying the icon to the right place and adding the
application meta-data to the central application database (via a XML
file that is also kept in a central place).
[Application][Tizen] Simplify the installation steps

We can keep the application binary (that will be a link to the xwalk-launcher)
binary inside a user created directory (data_dir), this allows for some
simplification.

Error are printed in the standard output, so the 'GetAppOutputWithExitCode()'
can print bettter error messages if installation/uninstallation fails.
[Application][Tizen] Change the effective UID of the application to 'root'

When adding the application metadata to the application
database (pkgmgr_parser_parse_manifest_for_installation), it is
required that the process has 'root'(0) UID so the
installation/uninstallation can proceed.
[Application][Tizen] Exit the application when the TERMINATE event is received

If we want the application to quit after it is terminated via the
Tizen task manager, we need to handle this event.

As Crosswalk will be following the unique name of the launcher process
and will kill the appropriate application when its launcher exits the
D-Bus session bus, simply calling exit() is enough.
[Application][Tizen] Be more tolerant of the parameters passed to xwalk-launcher

When the application is launched via the Tizen application
launcher (or via launch_app), it will be launched with more parameters
than we actually care, but if its argv[0] is a valid application ID,
that's all that we need.
[Application][Tizen] Separate paths for potencial conflicts

In the cases that we install files in the same path that the "old" way
would, use 'xwalk-service.'  prefix to keep these cases apart avoid
messing with old installations.
[Application][Tizen] Install a default crosswalk icon if no icon is provided

If the application being installed doesn't provides an icon, we install the
default Crosswalk icon as the icon for that application.
Merge pull request #1478 from vcgomes/tizen-use-pkg-helper

[Application][Tizen] Use helper tool to install applications when running as a service