refactor: scalar and complex renamed to real_scalar and complex_scalar respectively + concepts refactoring + electromagnetism fixes

docs/blog/posts/bringing-quantity-safety-to-the-next-level.md

@@ -34,8 +34,8 @@ A quantity character determines the properties and operations that can be perfor
 
 Quantities defined by the ISQ may be of the following characters:
 
-- scalar (e.g., _time_, _width_, _speed_, _apparent power_),
-- complex (e.g., _complex power_, _voltage phasor_, _electric current phasor_),
+- real scalar (e.g., _time_, _width_, _speed_, _apparent power_),
+- complex scalar (e.g., _voltage phasor_, _complex power_, _impedance_),
 - vector (e.g., _displacement_, _velocity_, _force_),
 - tensor (e.g., _moment of inertia_, _stress_, _strain_).
 

docs/blog/posts/isq-part-4-implemeting-isq.md

@@ -90,7 +90,7 @@ in one line of code. In the above code:
 
 !!! note
 
-    Some quantities may be specified to have complex, vector, or tensor character
+    Some quantities may be specified to have complex scalar, vector, or tensor character
     (e.g., `displacement`). The quantity character can be set with the last parameter of
     `quantity_spec`.
 

docs/blog/posts/isq-part-6-challenges.md

@@ -395,11 +395,11 @@ the same kind.
 
 Some quantities are more complicated than others. For example, _power_ has:
 
-- scalar quantities expressed in:
+- real scalar quantities expressed in:
     - W (watts) (e.g., _mechanical power_, _active power_),
     - VA (volt-ampere) (e.g., _apparent power_),
     - var (e.g., _reactive power_),
-- complex quantities expressed in VA (volt-ampere) (e.g., _complex power_).
+- complex scalar quantities expressed in VA (volt-ampere) (e.g., _complex power_).
 
 How should we model this? Maybe those should be two or three independent trees of quantities, each
 having its own unit?