fixed JodaTimeContextHolder to use a non-inheritable ThreadLocal and expose a reset method (SPR-7441); use of remove() even when being called with a null argument

Renamed org.springframework.ui.format package to simply org.springframework.format package; 'ui' is not adding any value - it makes the package name longer and also discourages use of formatters outside in other "non ui" environments where localized formatting of field values is needed.

ui.format system refining from RC1 feedback: Support for one format annotation applying to multiple field types, Printer/Parser building blocks for more flexibility, full Joda time formatting support, FormattingService as a service entry-point for clients to use