[Tizen] Verification name of a widget entry file

This patch contains function which verify name
of the widget entry file during installation.
Table contains list of proper names of the files
has been moved to constans.

BUG=XWALK-2983
@pozdnyakov Unfortunately, it can not be const char*, there is problem with arraysize( kDefaultWidgetEntryPages) function called in application.cc and xwalk_package_installer.cc. It not returns proper value.
We have some possibilities: this solution 
or 
const char*  kDefaultWidgetEntryPages[]
const int sizekDefaultWidgetEntryPages
or 
const char*  kDefaultWidgetEntryPages="index.html;index.htm;..."
and call split function in places where kDefaultWidgetEntryPages is used.
I suggest current solution.