Updated the calls to the Compara API
_create_cons_file() is part of _draw_structure()

This allows to have a proper variable with the name of the file that
contains the secondary structure. Otherwise, the code has to code the
filename in multiple places, hoping that they're consistent.
The path to the image is defined only once
The function that prints the alignment is independent from BioPerl
Extracted the method to get the data from the Compara db
New method to get the data from the Core db if not in Compara
"has_2ndary" is more precise than "can_r2r"
Merge pull request #70 from muffato/rnastruct

Extend the ncRNA secondary structure view