* adds support for null values to the ternary filter
This change adds a third optional argument to the ternary filter to
handle a null value. If the third option is specified null and false
are treated differently.
For instance, take the following example:
{{ enabled | ternary('no shutdown', 'shutdown') }}
If enabled == True, then 'no shutdown' is used.
If enabled in (False, None), then 'shutdown' is used.
With this change the following is possible:
{{ enabled | ternary('no shutdown', 'shutdown', omit) }}
If enabled == True, then 'no shutdown'
If enabled == False, then 'shutdown'
If enabled == None, then omit
* update documentation with example of filter
* update filter documentation example per comments
* fix logic error in user_guide example
1e68881c40