Add validation of ep-ratio

[kais-siala]

The problem is infeasible if the ratio between inst-cap-c and inst-cap-p is not ep-ratio.
Sometimes it is the case according to excel (in fact, I use outputs of one model year as input in the next year, so I am sure the ratio is correct), but not to pyomo after loading the values, probably due to rounding.

I personally solve this by rounding inst-cap-p to two digits, then multiplying it with ep-ratio to obtain an updated inst-cap-c. Maybe this could be included in the validation?