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.

The input seems to come from the network, so it could contain nul chars before the end of the buffer. How is that handled?