FUML13 — BasicInputOutput operations for reading and writing reals are missing

In the FoundationalModelLibrary::BasicInputOutput package, the TextInputChannel and TextOutputChannel classes have specific operations for reading and writing string, integer, boolean and unlimited natural values. However, there are no specific operations for reading or writing real values, which is inconsistent.

(Note that it is still possible to read and write real values by converting real values to/from strings, so this issue is not absolutely critical.)

Add readReal and writeReal operations

Agreed. A readReal operation needs to be added to TextInputCjannel, and a writeReal operation needs to be added to TextOutputChannel. In addition, the discussion of the behavior of the write operation for TextOutputChannel should be updated to mention Real values.