round min/max value for number entry parts to desired precision

see #296

For example: the correct answer to your question is 1.23456, but you want the student to give their answer rounded to 3 d.p.
Use the precision restriction to ask for 3 d.p., and the runtime now rounds off the correct answer for you so you don't have to write precround(1.23456,3) in the min/max value boxes
add non-strict option for numberentry precision

see #296
Merge branch 'master' into numberentry
non-strict numberentry precision restriction accepts any number of trailing zeroes <= limit.

e.g. if the question is "write 1.4 to 4 d.p.", then 1.4,1.40,1.400,1.4000 are all accepted.
see #296