[Fix] Read 'AppDir' path from recipe file. (v2)

[cabiste-dev]

Currently when building an image this tool only looks for the AppDir in the current working directory (unless --appdir is used) and completely ignores the path defined in the recipe file.
And when generating a recipe it only looks for the AppDir in the current directory ignoring --appdir argument.

This PR fixes that.

The hirearchy of importance is:

1. recipe.AppDir.path() (if defined and found)
2. --appdir argument (if used)
3. defaults to searching for AppDir in the current working directory

we don't talk about #326

[azubieta]

Thanks for helping!