Create a StringAllPositionsAreEqual factory

[MathyouMB]

For this generator we can randomize the length of the string and whether we are using "odd" or "even" positions.

Data:

<multiple-choice>
		<question>
		<![CDATA[
			Consider bitstrings of length 13. The positions in these strings are numbered as $1,2,3,\dots,13$.
			How many such bitstrings have the property that all bits at the odd positions are equal?
		]]>
		</question>
		<answer>32</answer>
		<answer>64</answer>
		<answer correct="correct">128</answer>
		<answer>256</answer>
	</multiple-choice>