Rework multi rate handling system

Rework multi rate handling system

In commits 6ca7b9c and bff19d9 have been developed a mechanism for
tasks timing, which is working properly when Auto or Multi threading (MT)
is selected. Unfortunatelly we have missed the option Single tasking (ST),
which should be checked instead of Auto or MT, because this mode is not yet
implemented.
When ST is selected in the model configuration, the timing becomes
completely wrong (besides a compilation warning reported in Issue #1150),
because the manually generated timers are colliding with the automatically
generated timers.

As a result, the code written in the mentioned commits has been moved from
rpp_srmain.tlc into rpp_mrmain.tlc, because some ideas will be used later
for implementing Multi tasking multirate system.

rpp_srmain.tlc content has been restored to the previous state, which was
working correctly with right model configuration.

Exit macro with error message has been added to the rpp_file_process.tlc
for wrong model configuration detection.

Configuration for all demos has been corrected.

Fixes: #1150