Opts: Make singleton; senseApi: check senseApiLibPath, get senseApiDescFn pointer.

* OptionsParser now has a singleton.
* We now use the cmdline opt -p <senseApiLibPath>, and search for
  the specified library in:
  * senseApiLibPath, then CWD, then the place where our executable
    is running from, and then finally we let the hosting OS do
    its own search.
* We now call dlsym() on dlopen()'d libs to to get the senseApiDescFn
  pointer.

hcore/include/opts.h

@@ -16,6 +16,12 @@ public:
     void dumpOptions() const;
     std::string getUsage() const;
 
+    static OptionParser &getOptions(void)
+    {
+        static OptionParser options;
+        return options;
+    }
+
 public:
     std::string senseApiLibPath;
     std::vector<std::string> senseApiLibs;