Adjusting plugin and csbi creation for updated YANG models

This MR addresses the following issue, which occured after updating YANG models and gathering them in one place:

• Plugin and cSBI creation fails because the models cannot be found while searching for them within the generate process

Additionally this MR changes the plugin creation within the controller. An additional file is expected csbiAdditions.go when a plugin/csbi is created. This results in no need for any additional adjustments to the generated gostruct.go file via go-templates.

Description

Related Issue

#209 (closed)

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.