Add the sigma types of category variants
Add initial and terminal categories

After    | File Name                             | Before
-----------------------------------------------------------
1m41.76s | Category/Equality                     | 1m41.97s
0m22.65s | Functor/Equality                      | 0m22.41s
0m14.58s | NaturalTransformation/Equality        | 0m15.15s
0m07.60s | Category/Morphisms                    | 0m07.16s
0m05.30s | Groupoid                              | 0m05.22s
0m02.48s | NaturalTransformation/Composition     | 0m02.26s
0m02.27s | Functor/CompositionLaws               | 0m02.10s
0m01.95s | SumPreCategory                        | 0m01.98s
0m01.75s | ProductPreCategory                    | 0m01.86s
0m01.54s | NaturalTransformation/CompositionLaws | 0m01.34s
0m01.31s | NatCategory                           | 0m01.30s
0m01.12s | InitialTerminalCategory               |   N/A
0m00.93s | BoolCategory                          | 0m00.89s
0m00.52s | SetCategory                           | 0m00.48s
0m00.33s | Common                                | 0m00.31s
0m00.28s | NaturalTransformation/Identity        | 0m00.28s
0m00.26s | FunctorPreCategory                    | 0m00.27s
0m00.26s | Functor/Composition                   | 0m00.19s
0m00.17s | NaturalTransformation/Core            | 0m00.14s
0m00.15s | Category/Core                         | 0m00.14s
0m00.13s | Functor/Core                          | 0m00.16s
0m00.12s | Peano                                 | 0m00.11s
0m00.11s | NaturalTransformation                 | 0m00.10s
0m00.10s | Category/Category                     | 0m00.12s
0m00.10s | Functor                               | 0m00.10s
0m00.09s | Functor/Identity                      | 0m00.10s
0m00.09s | Utf8                                  | 0m00.08s
0m00.09s | Category/StrictCategory               | 0m00.09s
0m00.08s | DiscreteCategory                      | 0m00.11s
0m00.04s | NotationsUtf8                         | 0m00.05s
0m00.04s | Notations                             | 0m00.05s
-----------------------------------------------------------
2m48.19s | Total                                 | 2m46.51s