LOGBACK-835 - make timestamp properties default to local scope. Can be overriden by setting scope attribute
LOGBACK-833 - allow previously defined properties (in local scope) to be seen by SiftingJoranConfigurator
 * implemented part two of Ceki's suggestion
 * add getCopyOfPropertyMap() to the PropertyContainer and thus InterpretationContext
 * use local properties that are ineffect at time of creation of SiftingAppender to seed the properties map used when creting the child appenders and properties
 * removed some generics warnings
 * in AppenderFactoryBase use List.subList() rather than "copy whole array then delete and re-shuffle elements"
LOGBACK-835 - corrected status message in timestamp
LOGBACK-833 - unit test improvements to check that a local timestamp property really was set
Merge pull request #111 from diroussel/LOGBACK-833-sift-variables

LOGBACK-833 Fixes for variables in sifting appender