Added information on CALIBER diabetes phenotype components.

Added a handful of phenotypes which were sourced from the CALIBER core phenotypes so this repository is self-contained.

Removed primary care phenotypes for cholesterol-related algorithms not used.
Updated implementation details for anaemias to only use confirmed diagnosis Read codes.
Removed pregnancy-related Read codes not used in study related to leiomyoma.

Removed rogue code for abdominal hernia