Implement the stx repomgr module so that the developer could manage
the repo on the host with the 'stx repomgr xxx' command.
Now support the action: [ list|download|sync|mirror|clean|remove_repo|upload_pkgs ]
Please refer to the more help information with the command
'stx repomgr --help'
Story: 2008862
Task: 43121
Signed-off-by: Zhixiong Chi <zhixiong.chi@windriver.com>
Change-Id: I27b649cfe941fa2275cee63a753ff08b239fcc4e