Change `protection` level of `ApplicationEngine.LoadContext`

[cschuchardt88]

Is your feature request related to a problem? Please describe.
ApplicationEngine.LoadContext has changed from protected to internal. It breaks neo-express and I'm sure other developers applications that use ApplicationEngine.

Describe the solution you'd like
Change the protection level to protected or public

@shargon @Jim8y

Where in the software does this update applies to?

• core