Sort out processing logic... Test output...
Trying to avoid an impossibly long if ---- else if --- else if ----
when parsing words. Split the recognition and processing of
operators, fractions numbers etc. etc. in to separate functions.

Does basic processing of fractions

Test output...

$ java -ea FractionCalculatorTest
FractionTestCalculator tests verbose output:
debug call to process with inputString =" 1/2   +  -1/4 "
debug word= ""
debug word= "1/2"
debug got a fraction=1/2 numerator=1 denominator=2
debug store fraction 1/2
debug word= "+"
debug got a operator +
debug word= "-1/4"
debug got a fraction=-1/4 numerator=-1 denominator=4
debug apply operator + to fractions 1/2 and 1/-4
test "Simple parsing and operation: input of " 1/2   +  -1/4 " should give "1/4". Actually "1/4" is output." passes.
debug call to process with inputString ="1/2 - 3/4"
debug word= "1/2"
debug got a fraction=1/2 numerator=1 denominator=2
debug store fraction 1/2
debug word= "-"
debug got a operator -
debug word= "3/4"
debug got a fraction=3/4 numerator=3 denominator=4
debug apply operator - to fractions 1/2 and 3/4
ERROR get FAIL for test "Simple parsing and operation: input of "1/2 - 3/4" should give "-1/4". Actually "1/-4" is output.".
FractionCalculatorTest: 1 tests FAIL.
Exception in thread "main" java.lang.AssertionError: FractionCalculatorTest failed 1 tests
	at FractionCalculatorTest.simpleTests(FractionCalculatorTest.java:52)
	at FractionCalculatorTest.main(FractionCalculatorTest.java:16)

Need to get rid of debug output.

The output of 1/-4 instead of -1/4. Shows a problem in Fraction class need to deal with in Fraction and FractionTest