[js] Add base support for pickContact functionality.
Add ContactFieldType constants
Change arguments order for find and pickContact methods.
[android] Add pickContact support for android
[wp8] Add pickContact support for Windows Phone 7 and 8
[ios] Add pickContact support for iOS
[windows8] Replace find method with pickContact,  treat find method as unimplemented on Windows 8
[windows8] pickContact now picks only one contact, similar to other platforms,
move contact conversion logic to separate function,
add requires to other modules.
[wp8] pickContact now picks only one contact, similar to other platforms,
move contact conversion logic to separate function,
change conversion logic to return proper cordova contact,
add requires to other modules.
[docs] Add pickContact info and sample app.