Add support for using stock title.tmd instead of making title.tmd if file exist

[wzhy90]

https://github.com/Jimmy-Z/twlnf/blob/master/arm9/source/tmd.c
Just like that, if stock title.tmd exist, use it and generate the signature ticket in SD:/ticket//.tik

Alos sdnand can run modified/region invalid dsiware, so we can simply skip invalid region check and sha1 check of .app file.

This is my fork: wzhy90/twlnf_sd@b995ef3#diff-fd92d51bd33848db6c20f8e986de3f07

After that, I can backup/restore the region free Nintendogs from china with the stock title.tmd and modified .app rom in Settings - Data Manager

[JeffRuLz]

I don't know much about tickets. What are the benefits of having them on CFW? Just backup/restore functionality?

[wzhy90]

If you want to use the stock title.tmd then you will need the ticket file, otherwise system will delete the title dsiware after boot. And using stock title.tmd is the only way to backup/restore in Data Manager.

[JeffRuLz]

I've been considering adding a custom backup/restore function, so it'd be easier to manage on a PC.

Idk, at the moment I'm not sure how to incorporate the feature you want. If you could make a fork I'd merge it.