custom resolution is disabled for batch fits

[butler]

Adrian Rennie pointed out that custom (pinhole or slit) is not enabled on the batch fit page. This was probably turned off on the grounds that it is unlikely that a custom smear would be the same for all files. However for slit smeared it is quite likely that it would apply to all files, while most batch fitting is probably going to be applied to a series of data taken at once at one configuration so even the custom pinhole is likely to be a reasonable choice.