Project generation should output a warning if parameter is not a list when a placeholder expects one

[Knetic]

Currently, if a placeholder has a join specifier (such as project.package[.], where [.] is the join), it will treat single-element parameters as if there were no join. However, this could lead to unclean practice where every parameter is given an unnecessary join specifier.

Example;

Hello, ${{=project.name[.]=}}!

With parameter project.name=fooject will produce "Hello, fooject!" as expected. But it will not warn the user that the join specifier is not required. All this placeholder needs is;

Hello, ${{=project.name=}}!

And the tool should warn the user of that.

[Knetic]

Done as of 8cde9c9