Support for custom Views location

[RosenPetrovFFW]

Hello,

We have a case where we use a custom Views location and this is not supported ATM, so I decided to create this PR.

In between, I noticed some potential improvement in the Context Culture configuration and added a commit for this as well.

#H5YR

[rickbutterfield]

@RosenPetrovFFW this looks great! I'll add a note to the README as well about overriding, just writing it here so I've got it somewhere...

"BlockPreview": {
    "ViewLocations": {
        "BlockList": ["/path/to/views.cshtml"],
        "BlockGrid": ["/path/to/views.cshtml"]
    }
}