add 2 columns in Cat.sql
change column's capacity in Cat.sql
refactor BaseAlertConfig
Merge pull request #327 from youyong205/master

refactor aggregation config
add default alert receivers feature
add BaseAlertConfig
merge newest code
Merge branch 'master' of github.com:dianping/cat
Merge pull request #328 from leonindy/master

add default alert receievr feature
Merge branch 'master' of github.com:dianping/cat
refactor config
modify the problem url filter