[Tizen] Make better split between Tizen and Tizen mobile codebase

There are generic and mobile specific parts of the code that could
be split or shared. This patch enables -Dtizen=1 by default and moves
mobile specific code under tizen_mobile and OS_TIZEN_MOBILE flags.
Merge pull request #1605 from alexshalamov/split_mobile_and_generic_tizen

[Tizen] Make better split between Tizen and Tizen mobile codebase