Introduce a do-not-inherit this attribute modifier

[psss]

Sometimes it might be useful to define an attribute just for the current node and disable for it inheritance. It could look like this:

description.:
    This long description is intended just for this node and
    should not be inherited to children.

I suggest to use a dot . as the suffix as it signalizes that something is finishing here. Ideas?

[psss]

This is a bit relevant to #14.

[lukaszachy]

Updated the title as we have /: {inherit: false} which breaks the whole inheritance from parents.