FIXED - #15: ContextPath is inconsistently saved as part of the
savedRequest 
- earlier, context path was dropped from plain page render requests but
stored for component event requests. The context path was later added
with Shiro's WebUtils.issueRedirect, remove that usage
- change the savedRequest logic to always save the context path with the
request
- always return 303 instead of 302 for saved requests (303 explicitly
calls for a GET redirect regardless of original request method type)
- deprecate LoginContextService.getXxxPage() operations, add new
getXxxURL() as replacements, in preparation for #16 and version 0.7.0
- implemement LoginContextService.removeSavedRequest() for completeness
- clean usage in LoginLink
- add test for saving ComponentEventRequest