Stix ipwatch v1.11

Adds support for STIX-based indicators for feature #1095.

From previous PR: #1096:
Ensured each commit compiles.
Modified WatchListData data structure in util-ipwatchlist.h to use a char* instead of a Signature.
Resolved comments from #1096 

From previous PR: #1060:
Organized and updated unit test function names to start with upper case letter in detect-watchlist.c and detect-smtp-indicators.c.
Modified InitWatchDataFully to properly invoke free.
Updated to meet QA standards.

What is the reason for manually constructing a json string here? All other code uses the proper json interface.