Hello!

I develop new payment gateway for IPS; I can easily create folder and .php in /applications/nexus/sources/Gateway, and it's even work! Settings strings easily created in DB and parse from it, but i cannot create new lang strings or new templates through this method 

Maybe someone say me: how i can create new app where extends default functionality IPS if this functionality requires, that some files be in some (specials) folders e.g. payment gateway, which must be in /applications/nexus/sources/Gateway.  Well, or at least, perhaps there is a way to create lang strings and templates that will be in the default folders? (like /applications/nexus/dev/html/admin/hosting);
(/applications/nexus/dev/lang.php) 

The same applies to new payouts methods, new type of item (in store), new payment agreements etc.

Good job creating a new gateway!

Unfortunately, presently it has to be shipped as you've seen (uploading the files to the appropriate location). In order to add new language strings, theme templates, settings, etc. you would need to create a plugin to "house" those things, even though the payment gateway itself cannot be solely distributed as a plugin since a file needs to be manually uploaded.

You can use this to create custom language bits:

or create your own; you just need to insert to the lang bits table. 

I easy solved this problem, @bfarber  is absolutely right. In addition to the file gateway, administrator must use special plugin which contains new templates, lang strings and more.

Thank you.