flow: switch it to use the eWoms parameter system

this has several advanges:

- a consistent and complete help message is now printed by passing the
  -h or --help command line parameters. most notably this allows to
  generically implement tab completion of parameters for bash
- the full list of runtime parameters can now be printed before the simulator
  has been run.
- all runtime parameters understood by ebos can be specified
- no hacks to marry the two parameter systems anymore
- command parameters now follow the standard unix convention, i.e.,
  `--param-name=value` instead of `param_name=value`

on the negative side, some parameters have been renamed and the syntax
has changed so calls to `flow` that specify parameters must adapted.

tests/run-regressionTest.sh

@@ -17,7 +17,11 @@ TEST_ARGS="$@"
 
 mkdir -p ${RESULT_PATH}
 cd ${RESULT_PATH}
-${BINPATH}/${EXE_NAME} ${TEST_ARGS} output_dir=${RESULT_PATH}
+if test "${EXE_NAME}" = "flow"; then
+    ${BINPATH}/${EXE_NAME} ${TEST_ARGS} --ecl-output-dir=${RESULT_PATH}
+else
+    ${BINPATH}/${EXE_NAME} ${TEST_ARGS} output_dir=${RESULT_PATH}
+fi
 test $? -eq 0 || exit 1
 cd ..