- expose isDisableInheritableForThreadPool/isEnableTimerTask
- improve test for DisableInheritableForThreadPool

disable Inheritable feature by using InheritableThreadLocal
can avoid potential leaking problem described in #100

add assert:
current thread's TTL must be exist when using DisableInheritableThreadFactory

- add DisableInheritableThreadFactory wrapper in TtlExecutors
- add Inheritable unit test

- move some plugins to pluginManagement
- default not create sources jar, speedup dev

- insertAfter method can execute as a finally clause
- but fail to cooperate with add local var(this is reasonable behavior)