Removed the For class, and alternative classes have been added (v3.0.0)

[simon-ritchie]

Since v3.0.0, the major version has been raised to 3.0.0 because the For class for loops has been dropped in this version.

Please use the following classes from now on:

• ForArrayIndices
• ForArrayValues
• ForDictKeys
• ForDictValues
• ForDictKeysAndValues

This change is supposed to make type-checking more robust.