MWA tile names are read incorrectly from the metafits file

[PyxieLouStar]

Currently when a metafits file is submitted, tile_names are taken from the metafits "Tile" field instead of the "TileName" field, yielding tile numbers instead of names in obs.baseline_info. If the metafits file is not submitted, the correct tile names are taken from the uvfits file and used instead.

[PyxieLouStar]

Actually it looks like the tile_names are always filled with tile numbers rather then names whether the field is taken from a metafits or a uvfits file. It might make sense to leave it as-is, maybe with a comment noting that we are storing tile numbers rather than names in the obs.baseline_info object. @bhazelton @isullivan any thoughts?