uBrowser: Reference EWK browser application

uBrowser: Reference EWK browser application

This is basically my attempt at implementing more usable test
application for for chromium-ewk. Currently efl_webview_app is rather
limited and it's codebase is messy. It's main adventage is it works on
both Tizen and desktop. Mini browser has a few more features but it
only runs on tizen. Personally, I consider it's code to be of similar
quality as efl_webview_app.

uBrowser on the other hand works on both tizen and desktop, has simiar
feature set on both platforms and tries to split the code into smaller
chunks that are hopefully easier to understand and maintain. Compared to
mini_browser it's currently missing 2 features:
1. It does not support vibration. (I could not get it work on
   mini_browser, but the code is there)
2. It does not have any find in page funcionality. (Mini browser has one
   button that allows users search for hardcoded word 'google')

What is more important however, uBrowser does support multi window mode.
It's possible to open/close/switch between windows. I consider this
feature important because I've started the whole project when I had to
debug some multi-window related problems and none of the existing apps
made it easy. After that I just kept adding new features whenever I needed
them and they were either not available or did not work well enough in
other apps.

The app is far from finished and it probably has a few bugs. Still, I
decided there is no point in keeping it for myself any longer. It's nicely
separated from other EWK components and does not take a long time to
build. Hopefully other people will add even more features to it. At some
point it may even replace old reference EWK apps.
Reviewed by: Antonio Gomes, Kamil Klimek, arno renevier

Change-Id: I5f9cbdc9cb9e6bd801d3d02feff1ad02e97569b5
Signed-off-by: Piotr Tworek <p.tworek@samsung.com>