Add Get Columns to for Model

[JarriqTheTechie]

Describe the feature as you'd like to see it
Add the ability to get a list of column names from the model.

What do we currently have to do now?
There is currently no way to do this.

Additional context
New feature should work like.

`class Post(Model):
pass

columns = Post.get_columns()
`

In the above case it would return all columns that would be returned from "SELECT * FROM Posts"
In other cases if selects is defined on the model it would return those columns.

Is this a breaking change? No