Don't rebuild file embeds if they haven't changed.

Change-Id: Ia3de5b5dc00341254b76b7adf88bf6038319690e
Merge "Don't rebuild file embeds if they haven't changed."
ui: add a custom BlobItemDemoContent renderer type, for demos

BlobItemDemoContent is a demo node type, useful for giving talks and showing
how a custom renderer can be invoked just by making a permanode, setting
its "camliNodeType" attribute to "camlistore.org:demo", and then changing its
background color with the "color" property or text with the "title" property.

Change-Id: Ib592471b785fde5750754bde3aa71eb8e2c10f3b
index: rename the reindex method to indexBlob, to be less confusing.

Also, upon server --reindex, check that no out-of-order blobs are
pending.  From a quick reading, they shouldn't be, but I'm curious to
see.  Will do a full reindex of my data later.

Change-Id: Idebf93cc264e55512afcfb99e47320dd0ae745d1