Add query method for task by candidate user or candidate group or assigneed

Many developer need it.

sql like below:
```sql
select distinct RES.* from ACT_RU_TASK RES inner join ACT_RU_IDENTITYLINK I on I.TASK_ID_ = RES.ID_ WHERE (RES.ASSIGNEE_ = ? or (RES.ASSIGNEE_ is null and I.USER_ID_ = ? or I.GROUP_ID_ IN (select g.GROUP_ID_ from ACT_ID_MEMBERSHIP g where g.USER_ID_ = ? ) ) )
```