[curve tool]: implement delete volume command

[cw123]

Describe the feature you'd like:

we'd like to support delete volume command in curve tool

delete is one of the commands to delete one volume.

• The implementation of the old tool is here：

https://github.com/opencurve/curve/blob/master/src/tools/namespace_tool_core.cpp#L58

• The old command:

delete : delete the file, to force delete, should specify the --forcedelete=true

$ curve_ops_tool delete --example
Example:
curve_ops_tool delete -mdsAddr=127.0.0.1:6666 -fileName=/test -userName=test -password=123 -forcedelete=true

• The new command we want:

curve bs delete --filename /curvebs-file-name --username username [--password password] [--forcedelete true]

If command sucess, print success.
If command failed, print failed, and the fail reason.

Teachability, Documentation, Adoption, Migration Strategy:

Refer to tool develop guide to get start, and paste the result of the command in pr.

Build compilation environment：https://github.com/opencurve/curve/blob/master/docs/cn/build_and_run.md

[shentupenghui]

i would like solve this