create "repair light" option [JIRA: RIAK-2334]

[matthewvon]

Part of the repair procedure is to open and read every .sst file. This is done to verify data CRCs and potential throw out corrupted files. However, there is a common use case of only desiring to rebuild the manifest file (such as manual deletion of old .sst files). Data is not considered suspect in this use case.

The goal is to create a flag that would allow a user to skip the read of all .sst files, only rebuild the manifest.

[matthewvon]

One of the things repair extracts while scanning the full .sst table file is the highest sequence number. That number is now recorded with Basho's .sst counters as of mv-expiry merge to develop (July 6, 2016). That is a key enabler of repair light.