Replace keywords_for_all_files global variable with an object attributed and add each keyword as an object attribute
Replace federstuff and feder with single variable feder
Change keywords_for_light_files from global variable to Feder attribute and add those keywords as attributes
Remove remaining uses of RA/DEC global variables
Convert overscan global variables to attributes of Feder
Eliminate glob (*) import from Feder.

Closes #31