Duplicate aliases on a Property should be an IllegalArgument

**Describe the bug**
Currently it is possible to add duplicate aliases during the creation of a Property and they are silently ignored. This is almost certainly masking a user configuration typo and should just be an error. For instance, this is allowed and the duplicate ignored:
`StrProp.builder().aliasIn("Str1In1").aliasIn("Str1In1").build();`

This also makes alias order ambiguous, which is a related ticket #581

**To Reproduce**
See the `PropertyBaseTest`

**Expected behavior / Actual behavior**
Exception thrown during construction to fail fast.