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-porv-acceptanceTest.sh

@@ -21,9 +21,14 @@ TEST_ARGS="$@"
 rm -Rf  ${RESULT_PATH}
 mkdir -p ${RESULT_PATH}
 cd ${RESULT_PATH}
-${BINPATH}/${EXE_NAME} ${TEST_ARGS} nosim=true output_dir=${RESULT_PATH}
+if test "${EXE_NAME}" = "flow"; then
+    ${BINPATH}/${EXE_NAME} ${TEST_ARGS} --flow-enable-dry-run=true --ecl-output-dir=${RESULT_PATH}
+else
+    ${BINPATH}/${EXE_NAME} ${TEST_ARGS} nosim=true output_dir=${RESULT_PATH}
+fi
 cd ..
 
+
 ecode=0
 ${COMPARE_ECL_COMMAND} -t INIT -k PORV ${RESULT_PATH}/${FILENAME} ${INPUT_DATA_PATH}/opm-porevolume-reference/${EXE_NAME}/${FILENAME} ${ABS_TOL} ${REL_TOL}
 if [ $? -ne 0 ]