refactor: quantity::count() renamed to quantity::number()

Resolves #259

docs/framework/conversions_and_casting.rst

@@ -179,7 +179,7 @@ code will not compile::
 
 To make it compile fine we have to either explicitly get the value stored in the quantity::
 
-    auto v = std::exp(quantity_cast<one>(10_q_m / 5_q_m).count());
+    auto v = std::exp(quantity_cast<one>(10_q_m / 5_q_m).number());
 
 or use a mathematical wrapper function from `units` namespace::
 
@@ -188,4 +188,4 @@ or use a mathematical wrapper function from `units` namespace::
 .. important::
 
     Always remember to explicitly cast the quantity to the destination unit with `quantity_cast` before
-    calling `quantity::count()`!
+    calling `quantity::number()`!

docs/framework/quantities.rst

@@ -336,7 +336,7 @@ will print ``50 %`` to the console output.
 
 Again, according to the ISO definition "such quantities convey more information than a
 number". This is exactly what we observe in the above example. The value stored inside
-the quantity, the text output, and the value returned by the `quantity::count()` member
+the quantity, the text output, and the value returned by the `quantity::number()` member
 function is ``50`` rather than ``0.5``. It means that dimensionless quantities behave
 like all other quantities and store the value in terms of a ratio of a coherent unit.
 This allows us to not loose precision when we divide quantities of the same dimensions