[Validator] added ratio precision to image validator

[nkt]

Q	A
Bug fix?	no
New feature?	yes
BC breaks?	no
Deprecations?	no
Tests pass?	yes
License	MIT

In my current project I've added validation rule, that image aspect ratio should be equal 1.33. But php gives more precision if calculate 4/3. So I have to add hack: minRatio="1.332", maxRatio="1.334".
This PR allow specify precision for image aspect ratio, using ratioPrecision option.

[webmozart]

Thank you for this PR! I'm not sure this is necessary. Wouldn't it suffice to fix the precision to 2 or 3 digits?

[nkt]

@webmozart do you mean always round ratio?

[fabpot]

@nkt Instead of adding yet another option, what about being less strict when checking the precision? If you set the ratio to 1.33, we would only check the first X digits, so 4/3 == 1.33333, but the comparison would be on 1.33 and would match your ratio.

[webmozart]

Replaced by #11928.