Support for Epsilon on double and float

[GooRiOn]

Currently we don't support Epsilon in extensions for double and float. The suggestion is that each method should have default parameter like:

(this IValitRule<TObject, double> rule, double value, double epsilon = 0.0d)

so user can specify it, but it's not required. Each method should then consider this number in the calculations. Need to applied for:

• IsGreaterThan()
• IsLessThan()
• IsEqualTo()
• IsPositive()
• IsNegative()
• IsNonZero()