MobleyLab/FreeSolv: Version 0.52

• Remove redundant molecule mobley_4689084 (which duplicates mobley_352111 , had the same experimental value, and a calculated value within uncertainty)
• Add utility functionality to easily check for duplicates; rebuild database after removing above duplicate and checking for others
• Update reference for calculated values to refer to the J Chem Engr Data reference.

These changes were made to the repo some eight months ago but apparently I forgot to make a new release at that time.