Fix status section out of order problem

mutiple status.go in go/cmd add status section in vt status server
for system monitoring purpose. However, the problem is they use init
function and may cause potential section out of order problem on
status page if there is another place to also add a new section.

The fix is to introduce a pluggable hook in each status.go so that
whenever another place want to add a new section, it could do so by
assign the hook in its init method.
change dbconfigs API to accept specific credentials

1. Add a DBConfigFlag bitmask param to RegisterFlags and
   Init methods
2. Add a return value for RegisterFlags method to indicate
   registered DBConfigFlag
3. Add dbconfigs test
rename splitsPerShard to splits

Vtgate's SplitsQuery only supports total number of splits
and calculate per shard split number based on it. Therefore,
rename VitessConf and VitessInputFormat to reflect this behavior.
Implement etcd flavor for TopoServer.
Merge pull request #237 from yaoshengzhe/fix_mr_shard_param

rename splitsPerShard to splits
Set a default topo server flavor for integration tests.

There are two flavors now, so the default can't be inferred.
Merge pull request #238 from youtube/etcd

Implement etcd flavor for TopoServer.
Rewrite imports for golang subrepositories.

As per this announcement:
https://groups.google.com/forum/m/#!msg/golang-announce/eD8dh3T9yyA/HDOEU_ZSmvAJ
Removing waitTime from tmclient streaming RPC calls.
Merge branch 'master' of github.com:youtube/vitess
Using context in all the topo server lock methods.

So we can remove timeout and interrupted.
Removing global wrangler interrupted channel, now just
cancelling its context.
Fixing capitalization of error messages.
Merge branch 'master' into golang-x
Merge branch 'golang-x'
Merge branch 'master' into replication
Fixing context path.
Removing dummy context.
Few fixes after review, and fix the tests.
Caling the cancel() function for context more.

Even if err != nil.
Merge pull request #242 from youtube/replication

Replication