Fixes #361
Fixes #361

Allow _getStringWinRT to fallback to the "strings" global when resources cannot be resolved.

This allows users to include WinJS in their package and get the default English strings by including base.strings.js and ui.strings.js.

IveWong/winjs,Guadzilah/winjs,nobuoka/winjs,IveWong/winjs,edrohler/winjs,CensoredUser/winjs,CensoredUser/winjs,ladyinblack/winjs,IveWong/winjs,gautamsi/winjs,rigdern/winjs,ladyinblack/winjs,jmptrader/winjs,KevinTCoughlin/winjs,rigdern/winjs,ladyinblack/winjs,KevinTCoughlin/winjs,rigdern/winjs,GREYFOXRGR/winjs,PaulWells/winjs,PaulWells/winjs,PaulWells/winjs,jmptrader/winjs,gautamsi/winjs,CensoredUser/winjs,kevinwsbr/winjs,nobuoka/winjs,nobuoka/winjs,Guadzilah/winjs,edrohler/winjs,KevinTCoughlin/winjs,grork/winjs,edrohler/winjs,jmptrader/winjs,grork/winjs,GREYFOXRGR/winjs,grork/winjs,kevinwsbr/winjs,kevinwsbr/winjs,gautamsi/winjs,GREYFOXRGR/winjs,Guadzilah/winjs