Only invoke the split service for a filter that requires splitting

[jzonthemtn]

Some of the filters don't require input text to be split while others do. The splitting should be smart enough to know that if all of the filters in the policy don't require splitting, then don't split. Conversely, if there is at least one filter in the policy that does require splitting, then split the input text.

This change would be in PhileasFilterService to look at the split config and the policy to determine if splitting is actually necessary.