Fix reset most visited sites functionality.

Fix reset most visited sites functionality.

[Issue]    https://bugs.tizen.org/jira/browse/TT-175
[Problem]  Reset most visited sites isn't working.
[Cause]    Not implemented.
[Solution] Implemented setting site visit counter to 0 and
           displaying only sites with counter grater then 0.
[Verify]   Visit some sites, go to settings, press Reset Most Visted
           Sites button, check if on new tab most visited sites are empty.

Change-Id: I05d44043744a1b7859b23df282dfb53745fb894d
Signed-off-by: Dariusz Frankiewicz <d.frankiewic@samsung.com>