replace load_gcfs function

[CunliangGeng]

Function load_gcfs should be replaced with new independent functions from genomics.py.

• replace load_gcfs function with independent steps

Step 1: load all strains
Step 2: load all bgcs
Step 3: load all gcfs
Step 4: connect bgc to strain with map_strain_to_bgc
Step 5: connect gcf to bgcs with map_bgc_to_gcf
Step 6: filter_mibig_only_gcf
Step 7: get clean gcfs, bgcs and strains with get_bgcs_from_gcfs and get_strains_from_bgcs

[CunliangGeng]

Solved #185.