update versions under scenario

update versions under scenario

1. post, add one or more new versions
2. update, replace existed version as a totality
3. delete, delete one or more versions by name
4. in post&update, if schema is not consistent with ScenarioVersion model,
BadRequest will be raised(only extra keys will be detected currently)
5. in post, if project already exist, return Conflict with already exist
message
6. in update, if a version appears more than once, also return Conflict
with already exist message
7. add update with conflict unittest for projects

Change-Id: I0d2c8a5567f3abce7b0313a64e18303af02cc002
Signed-off-by: SerenaFeng <feng.xiaowei@zte.com.cn>