[minor update of SandwichFeatures]
- make a resfile to design surface heading or loop residues
- Force to write_strand_AA_distribution_files only after count_AA_with_direction
- much better (easier to understand) namings (like get_vector_loop_AA_distribution and
get_vector_strand_AA_distribution, write_loop_AA_distribution_files_)
[integration tests]
- should not change other than features and features_database_schema (if any)