salt.pillar.file_tree: Optimizations, deprecate raw_data
salt.pillar.file_tree: Optimizations, deprecate raw_data

This modifies this ext_pillar to read in the file file_buffer_size bytes
at a time. It also removes needlessly duplicated code for dictionary
merging with salt.utils.dictupdate.merge().

Finally, the 'raw_data' argument is poorly-named and does not describe
very well what it actually does, so I have renamed this option to
'keep_newline'.

saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt