[webapi-usecase] Add pluggable step for 48 usecase and remove 28 usecase

- Add pluggable step info for 48 usecase
- Remove 28 usecase beacuase of repeating with demo-express

Impacted tests(approved): new 0, update 48, delete 28
Unit test platform: [IVI]
Unit test result summary: pass 48, fail 0, block 0
[webapi-usecase] Remove 28 usecase items in tests xml files

- Remove usecase items in tests.full.xml, tests.android.xml and tests.tizen.xml
Merge pull request #958 from xinliux/xinliux/usecase/stepinfo

[webapi-usecase] Add pluggable step for 48 usecase and remove 28 usecase
[misc]update xwalkctl to pkgcmd

Impacted TCs num(approved): New 0, update 4, deleted 0
Unit test platform: [tizen]
UT result: Pass:4, Fail 0, block 0
Merge pull request #968 from linshen/shenlin/misc/updatexwalkctl

[misc]update xwalkctl to pkgcmd