change uid to userid

(All tables which include created and updated)
1. created date problem: create date format has a problem when update
time changes
"template" : '#=convertTime(created)#'
NaN/NaN/NaN NaN:NaN:NaN
but create time is not changed in the database

2. uid can not be created in issues/session/occurences table (solved by
changing uid to userid)

3. each cell only can be editted once in issues/session/occurences table
(solved by changing uid to userid)

(issues table)
4. when creating a same issue(same title, description pid), it will
display an empty row(not write into database, old problem, see it before
the http
200 problem)

(session table)
5. it seems that there is a build-in sessions table, so we keep to use
'session' table instead of 'sessions' (there is a build-in table
seesion)