1) Add in SharingStringPack to make UpdateString only create/update string token...

1) Add in SharingStringPack to make UpdateString only create/update string token in the String Packages that shares String Package with each other. For a String Token to be updated in a Package, TagGUID must be the same and SharingStringPack need to be true too.
If a package list has both String Package and Form Package registered, the Create/Update of String Token will only be done in this Package List.
2) Add in Doxygen Function headers.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@6736 6f19259b-4bc3-4df7-8a09-765794883524