Adds option for adding a resolved url or filepath for stream downloading

[havok2063]

This PR closes #55 and adds the option using sdss_access stream downloading if you already have fully resolved urls or filepaths instead of a set of path keyword arguments. It adds a new method .add_file that accepts either a filepath, url, or path location and reconstructs the correct input to stream.

access = Access(release='DR17')
access.remote()
f = '/Users/Brian/Work/sdss/sas/dr17/manga/spectro/redux/v3_1_1/8485/stack/manga-8485-1901-LOGCUBE.fits.gz'
access.add_file(f, input_type='filepath')
access.set_stream()
access.commit()

or a resolved url

access = Access(release='DR17')
access.remote()
u = 'rsync://dtn.sdss.org/dr17/manga/spectro/redux/v3_1_1/8485/stack/manga-8485-1901-LOGCUBE.fits.gz'
access.add_file(u, input_type='url')
access.set_stream()
access.commit()