Refactored IPage/AbstractPage. Moved copy/pasted methods from
IPageWithTable and IPageWithNodes to IPage. Moved T for table-type to
IPage, since all pages have a table now. Added convencience methode
getPageFor() to IPage. Removed a lot of instanceof Statements used to
distinct between getTable() and getInternalTable(). Added class
OutlineEvent (extends TreeEvent). 

Change-Id: I60c7c09be566933d3ef447d1bc319abe80928b9c
Signed-off-by: André Wegmüller <awe@bsiag.com>
Reviewed-on: https://git.eclipse.org/r/38648
Tested-by: Hudson CI
Reviewed-by: Jeremie Bresson <jbr@bsiag.com>