Scope support

[brendt]

This PR is based on model-support for review. #1 must be merged before this one can target master.

[brendt]

Some questions:

• Could we improve the naming of resolveEnumerables and make it protected?
• Should we use the spread operator instead of arrays? Eg Blog::whereEnum('status', StatusEnum::DRAFT(), StatusEnum::PUBLISHED()). I gave this some thought and decided arrays are more clear, but I'd like to hear your input.

[Gummibeer]

After spatie/enum:2.1.0 we don't need the mapping of values in the scopes anymore. Instead the scopes should also respect the possible cast to integer - introduced in 61e93c9 .
I would also like to have a whereEnum($column, $value) and a second whereInEnum($column, $values) - same for not. I think that it should be possible to have a scope which would fail if multiple values are passed. So far I know the default laravel where methods also don't auto-switch depending on the argument type(?).

[Gummibeer]

@brendt I've opened this PR because it's now on master level and I've also added the missing or scopes.

[Gummibeer]

@freekmurze could you check this PR? @brendt and I have written the code.

[freekmurze]

Just one little nitpick