new defaultfilter wordcap: converts a string into titlecase but respect ...

Related to ticket https://code.djangoproject.com/ticket/21693

The defaultfilter title may in many cases be an issue to obtain a correct titlecase, for instance if the title contains acronyms or abbreviations. For instance, "SMS count"|title will display "Sms Count" which is not the desired result.
The defaultfilter wordcap try to provide a filter for this.
"SMS count"|wordcap -> "SMS Count"