added various longslit related tasks
added mhvk's copper argon line list
added some of MHVK's documentation
added the longslit arcs setup.
fixed wrong keyword
linking longslit arcs procedure finished
in the process of implementing longslit calibration
updated representation for longslit
in the process of saving the wavelength calibration to the database
finished the wavecal. updated the documentation
Merge pull request #43 from wkerzendorf/gmos/longslit_wavecal

[WIP] longslit wavecal