Re #198: Add slots with counts to units * Remove old Min/MaxNumber/Percentage for equipment and replace with limits * Refactor equipment selections and remove "numeric for ratio" as the limits handle the upper/lower limit differences * Stop equipment selections taking an amount of 0 for out of range amounts * Add "IsValid" property for selections * Removed use of "-1" as an 'infinity' limit - now use 100% as a more correct value * Change "unlimitedSize" limit in schema to "unitSizeLimit"