adding min() and max() filters for use in templates

In the process of trying to make some of my configuration file templates more dynamic to handle different configurations for different environments I ran into a couple of cases where a `min()` and `max()` filter would have been extremely useful. Basically I wanted to be able to say "derive this value from other host specific values, but never have it go below X (or above Y). I was able to work around it by having some ugly nested if/else stuff. But having a `min()` and `max()` would have made it much simpler.

It basically works just like the python builtins operating only on lists:

```yaml
- hosts: localhost
  connection: local
  gather_facts: false
  tasks:
    - debug: msg="min 1 - {{ [2,3,1] | min }}"
    - debug: msg="min 3 - {{ [9, 8, 12, 3, 4] | min }}"
    - debug: msg="max 5 - {{ [2,5,1] | max }}"
    - debug: msg="max 12 - {{ [9, 8, 12, 3, 4] | max }}"
```