[FAB-13381] Update dev mode documentation
[FAB-13381] Update dev mode documentation

- Update a chaincode path and keep it a bit vague about
  the exact location of the config file.
- Add an environment variable when start peer dev-mode

Change-Id: Ie5ef5f1399efa5960373b984223209132c72cd96
Signed-off-by: kuro1 <48dcee1f1fa376d94f32abe2f5bab8b3cea0ab35@qq.com>
(cherry picked from commit 274ce1fbe1c9de4eaf3b5fb9df7a8cb4c280d022)

xixuejia/fabric,xixuejia/fabric,xixuejia/fabric