* Hide the "randomize filename" checkbox on the index and the "filename"
text box on the paste page
* Update API documentation to show random filenames in examples
* Don't force a random filename when overwriting with a valid delete key
* If a filename already exists and a random filename is being used, keep
generating new random filenames until one doesn't exist instead of using
a counter
We can use the Host property of the request and the X-Forwarded-Proto to
infer the site URL. To reduce complexity, the path is not inferred, and
it is assumed that linx-server is running at /. If this is not the case,
the site URL must be manually configured; this is no different than it
was before.
This should protect against cross-site request forgery without the need
for cookies. It continues to allow requests with Linx-Delete-Key,
Linx-Expiry, or Linx-Randomize headers as these will not be set in the
case of cross-site requests.