Split some wikis into more shards

The goal is to keep the shards under 2gb where possible but to have less
than 20 each.  20 is pretty arbitrary at this point but 2gb helps with
maintenance.  If the shards are too big they are a pain to move around.

DEPLOYMENT: This won't take effect until the modified wikis are inplace
reindexed but this isn't important enough for us to do one.  We'll catch
this when we have results or space related reason to reindex everything.

Change-Id: I15d6a8da6d2a879c624f5ce01caa906c704a74b0
Start building the Cirrus index for huwiki

Add huwiki with shard counts of cawiki because they have similar page
counts.
Update some notes.

Change-Id: Ic23cc94599922f906816bc7a6bf5f15d15760760
Merge "Start building the Cirrus index for huwiki"
Merge "Split some wikis into more shards"