libvbucket: Substitute localhost marker in the config

This marker might appear since server release 2.5 as part of CCCP

More info:
* http://review.couchbase.org/29996
* http://review.couchbase.org/30067

Change-Id: I2a27a89501dd72563f7aa7e7da911e174c4565a8
Isolate HTTP bootstrapping code

Change-Id: Ibba093ec65d35b86295292447ea7f931c2258e52
Refactor internal configuration struct

It introduces API for pluggable bootstrap workflows

Change-Id: I1742b31089bfe5422b88a015b8891c4d20b57589
Extract function to pick node from backup list

* move external loop into the function
* allow to specify default port number

Change-Id: I90de13394a6becc1fe1baf7ed740af92df2466e6
CCBC-234 Bootstrap with CCCP

Change-Id: I96e91180f06b87e92ac1acee2c44dead1a2503af
CCBC-234 Use CCCP protocol to update vbucket configuration

Change-Id: I1fb24cee6ad9c6c4c77f4ac9f192215b846fe488
CCBC-234 Add lcb_cntl command to determine source of configuration

Change-Id: I933558ffe4a20eedca6e03ee7bf3d2dfe0e11ab0