improve auto_design selection of raman
improve auto_design selection of raman

-separate edfa and raman_list of acceptable amplifiers to better
customize criteria between edfa and raman amplifiers
for example min gian requirement: no extended min gain range for raman
amplifiers because there is always an edfa solution, which is better for
small gains.

Signed-off-by: Jean-Luc Auge <ff93e793a4ae3350e3b728274a021e7856e8c6b3@orange.com>

Telecominfraproject/gnpy