add ResourceExistsPropertyDefiner
Introducing AbstractDiscriminator base class to avoid repeated start()/stop() implementation in each concrete Discriminator
Support attribute "optional" in include element

Support attribute "optional" in include element to prevent errors on
inclusion of non-existent files without requiring Janino and
FileExistsPropertyDefiner.
fix logback-767

 StatusListener has two instances OnConsoleStatusListener and instance by
 seted classname.
 The second be Judged that is ContextAware and LifeCycle's implement and start it.
 but The first is not to Judged.

 all StatusListener must be Judged and start it.
more refactoring, added unit tests
make all tests pass
make the AppenderFactory related code in c.q.logback.core.sift suck less
more unit tests
more unit tests
allow timeout to be specified as a duration
updates to documentation
Merge pull request #115 from bjhanfeng/logback-767

fix logback-767
Merge pull request #89 from twbecker/LOGBACK-230

Fix for LOGBACK-230 - Support attribute "optional" in include element
fix LOGBACK-230
preparing relase 1.0.12
added the release date
next version will be 1.1.0
Merge pull request #57 from xuhuisheng/master

add ResourceExistsPropertyDefiner
Merge pull request #87 from nurkiewicz/abstract-discriminator

Introducing AbstractDiscriminator base class
added ResourceExistsPropertyDefiner, doc update