Set Length Limit on SiteCD

Stacey reported a few months ago that:

One other thing I just noticed with [the encounter views] are that the variable length is set to $8000 for SiteCD. My code is truncating that and sending me a warning which is fine, but given our space issues on the server, perhaps we should consider adjusting that in the view?

By calling left(..., 6) we can limit the size assumed by the view to only six characters. I believe this should be enough space, but we will keep an eye on this field to see if it should be wider in the future. Most SiteCD values are only 3 or 4 characters.

@jcd71 can you take a look and let me know if this looks fine to merge?