remove GetBoolArg() fDefault parameter defaulting to false

- explicitly set the default of all GetBoolArg() calls
- rework getarg_test.cpp and util_tests.cpp to cover this change
- some indentation fixes
- move macdockiconhandler.h include in bitcoin.cpp to the "our headers"
  section

src/util.h

@@ -390,7 +390,7 @@ int64 GetArg(const std::string& strArg, int64 nDefault);
  * @param default (true or false)
  * @return command-line argument or default value
  */
-bool GetBoolArg(const std::string& strArg, bool fDefault=false);
+bool GetBoolArg(const std::string& strArg, bool fDefault);
 
 /**
  * Set an argument if it doesn't already have a value