apply constraints to names for tasks and task instances in resource configuration

The same rules as for IEC identifiers are applied.
- no non-lating characters, ...
- no IEC keywords
- check for duplicate names in resource configuration

closes #19

BEREMIZ_OBJS = $(BEREMIZSRC:.c=.o)

all: warn some_binary
	@echo "*** all done ***"

warn:
	@echo "*** Sample Makefile, does nothing ***"

some_binary: $(BEREMIZ_OBJS)
	@echo "* Would link $^ -> $@"

%.o: %.c
	@echo "* Would compile $< -> $@"