cleaned up the general preparation of fits files
skipping preparation if prepared _fits exists already.
added sensible defaults for the prepare function
first trial of extraction
first trial of extraction
Merge branch 'development' of github.com:geminiutil/geminiutil into gmos/reduction

Conflicts:
	geminiutil/gmos/basic/extraction.py
changed to science_sets
added get_science_slice and moved extraction
get_readnoises added
added default_trace_position to slice object
Extraction using more pre-defined values
Rename output spectrum columns
added default_trace_position to slice object