Chunk reindexing/index regeneration

[Vlad1mir-D]

Another way to eliminate the effects of #70 and a part of repo maintenance process

[Vlad1mir-D]

Reindexing will be implemented in future versions, GC works properly now.

[jamespharaoh]

I think that it should also be possible to balance indexes, creating a small number of files, configurable by some parameter - eg chunks per index.

In my case, I have a huge number of index files, and these are accessed over NFS, which adds a per-file latency which is at some point going to be crippling.

I'm not sure if the existing patches address this or not, if so please let me know and, if necessary, let's update the documentation to make this more discoverable.