rename SomeReal to SomeFloat

[krux02]

The SomeReal types were the superset of all Float types. That is not only inconsistent with the names, but it is also wrong. Here is a list of reasons why calling floating point numebrs real (ℝ) is wrong.

∞ ∈ Float
∞ ∉ ℝ
NaN ∈ Float
NaN ∉ ℝ
ℚ ⊂ ℝ
Float \ {NaN, ∞, -∞} ⊂ ℚ
Float ∩ ℝ ⊂ ℚ

In words:

• infinity is a valid floating point value, but it is not a real number
• nan is a valuid floating point value, but again it is not not even a number at all, especially not a real number.
• Leaving out the special values of float, all that is left is a subset of the rational numbers.
  Or in other words, if you take all floating point numbers that are also real numbers, there is not a single value left, that would justify to call this number type "real numbers".

Thanks to deprecation mechanisms in Nim, this change doesn't break any code.