Virology changes

*  Lots of refactoring of existing code to axe out unused shit. Details in https://github.com/comma/Baystation12/commit/1820a227a14b606a0a4acf9e55feacb4c47b6c4a and  https://github.com/comma/Baystation12/commit/5703b8089d683e70aed7d360783ef9c3d9dd1324
*  Changed way viruses are stored in mob, from single var to associative list (ID -> virus), which allowed for multiple viruses in same mob.
*  Added new viro machine - centrifuge. Its functinos are sxtracting of viruses and antibodies from blood sample vials.
*  Cure machine and isolator are removed from map because their functions are now divided between centrifuge and incubator (dish -> blood transfer)
*  Changed way symptom's 'severtiy' is decided for randomization procs from typecheck to var, since former caused there to be duplicated of syndromes only differening in severity typepath.
*  Added a few new syndromes, inculding brittle bones, adrenaline generator (stolen from TG's advanced viruses), balding (ditto), limb shutdown, DNA damage. Every stage now has at least one beneficial syndrome.
*Rest of commits are from master.