Store: save NeedleMapKind value in Store
VolumeServer: add store task manager interface
Volume: rename `CleanReader` to `PureReader`
Makefile: format code before build
joinmessage: add `GolobalSetting` in join response
*: simplify code use `gofmt -s`
The volume TTL and file TTL are not necessarily the same. as long as
file TTL is smaller than volume TTL, it'll be fine.
volume TTL is used when assigning file id, e.g.
http://.../dir/assign?ttl=3h
file TTL is used when uploading