KDL layouts: Problematic node names

[raphCode]

#1759
This is sort of an oddball problem, since users probably have to try to hit this problem, but I reported it nonetheless.
More pane node names can be defined than make sense.
We might display a more meaningful error that hints at quoting if that resolves the issue or forbid certain names altogether.

I have tested this only with pane template names but I am sure there can be more places where these problems apply.

Empty string

layout {
    pane_template name="" {
        command "ls"
    }
    ""
}

works, but that seems strange somehow

Numbers at the beginning

layout {
    pane_template name="0test" {
        command "ls"
    }
    0test
}

Kdl Deserialization Error
Quoting the second 0test works.
Plain number without letters are also affected.

Special characters

layout {
    pane_template name="hello(test)" {
        command "ls"
    }
    hello(test)
}

Failed to deserialize KDL node.

Basically the same case as with numbers, except now the special characters cause also trouble when they occur in the middle of the node name.
Quoting works again.
I haven't tested this exhaustedly, but I would guess there are a lot of special characters that may cause trouble.

[imsnif]

Btw, for the record !@#$%^&* is a valid template name and runs as expected ;P

[imsnif]

Fixed in #1831