Support feature type ontologies for control, display, and analysis of sequence features

Currently, Jalview groups, filters and renders features according to their type string, however different feature sources employ different strings for the same feature type - either trivially (e.g. disulpfide_bond vs disulphide_bond), or more dramatically (e.g. cross_link and covalent_ligand to link two sites).

* Jalview should group features regardless of trivial variation
* Jalview should also offer display controls that take advantage of categorical groupings - e.g. show/hide all types of disorder features, all types of ligand-binding features, or all types of conformational shape (sheet, helix, turn) features.
* Jalview should appropriately display and analyse features according to their type (e.g. JAL-2327 - pairwise contact features should be treated as a pair of positions, not a range defined by start and end positions).