Allow replace filter on non-strings

[jasmith-hs]

Unlike other filters, the ReplaceFilter does not check if var instanceof String before casting it to a String. This results in a FATAL error if something besides a string is passed into the filter. I have seen a template that actually makes use of this logic unintentionally with code like {{ my_list.append(obj)|replace(true, '') }}. So, in order to fix this bug while maintaining the same output for legacy templates, this adds the functionality to the replace filter of calling toString() to allow it to be called on non-string objects.

Since the String class in Java is final, and String.toString() returns this, this will not change the functionality for any replace filtering on strings as the filter is intended for. However, using this filter on something like a boolean or a number will call toString on the object to convert it to a String, rather than throwing a ClassCastException and resulting in a FATAL error.