Merge pull request #312 from bronze1man/pr-orm-querytable-nil-ptr-struct

[orm] QueryTable with nil ptr struct
fix #302
add func InsertFilter(pattern string, pos int, filter FilterFunc) *App to replace AddFilter
pos can be const:
    BeforeRouter = iota
    AfterStatic
    BeforeExec
    AfterExec
    FinishRouter
replace filterPos to pos
eliminated improper comments
Merge pull request #314 from shavac/master

add function InsertFilter to replace AddFilter by using int const to determine filter position
beego.Context.Abort return immediately

* add common 4XX/5XX HTTP exceptions
Merge pull request #317 from pengfei-xue/master

beego.Context.Abort return immediately
fix type
fix #316
fix param to params
fix test
add server host:port info when starting app
Merge pull request #318 from pengfei-xue/devel

add server host:port info when starting app
fix #315
#313
session & orm  register called twice for driver mysql
update docs
fix _ "github.com/go-sql-driver/mysql"
orm add test about CustomField