VimwikiGoto: Support wiki pages with spaces

[sstallion]

This PR updates :VimwikiGoto to support opening wiki pages with spaces in the name.

[tinmarino]

Perfect to me:

Just one byte to replace the parameters command from by so that argument is quoted, anyway only the first argument is considered.

But this one byte is consolidated by nice test.
Thank you @sstallion

Can someone else please merge (rebase better say): @brennen , @chipsenkbeil ?

[chipsenkbeil]

I'm not that familiar with <q-args> versus <f-args>. Reading through the documentation, it sounds like <q-args> will produce a single argument whereas <f-args> breaks up by the space. The actual impl of vimwiki#base#goto only uses the first argument as part of the full path and an optional second argument as the anchor, so I think the above change makes sense and works better.

Since none of the tests fail, we can give this a go.