Allow node creation with default configuration (i.e. no <configure/>)

[ashward]

Brings the server more in line with XEP-0060, and fixes #200 by allowing node creation without specifying a configure element.

[imaginator]

Thanks Ash. I'll defer to @lloydwatkin's review - but this sounds sensible.

[lloydwatkin]

Hi @ashward sorry for taking so long to look at this, need to work out the consequences for later configuration updates and for publishing before configuration has taken place.

[imaginator]

@lloydwatkin wouldn't it make sense to always populate the config - even if with default values and null strings for title and description. Then if someone does pass a config option it overrides the default?

[lloydwatkin]

I still need to look into this as we (read: I) made some changes around node format and updating after its been set.

[lloydwatkin]

Sorry this has been so long @ashward, could you merge in master and I'll get into master ASAP. Looks like the work around preventing node content type changes when there's posts was discussions rather than actual code, so I'll bear this PR in mind when I add that functionality.