Rename the template_for header.

C++26 (I hope) is supposed to have this syntax:

```
template for( const auto &element: aggregate )
{
	...;
}
```

Thus, I've adjusted this gadget to have a similar name, to enable
simple mechanical code changes.  From Alepha, you'd use it
thus:

```
template_for( aggregate ) <=[&]( const auto &element )
{
	...;
};
```

IOStreams/OStreamable.h

@@ -7,7 +7,7 @@ static_assert( __cplusplus > 2020'99 );
 #include <ostream>
 
 #include <Alepha/Capabilities.h>
-#include <Alepha/template_for_each.h>
+#include <Alepha/template_for.h>
 #include <Alepha/string_algorithms.h>
 #include <Alepha/delimited_list.h>
 #include <Alepha/Concepts.h>