Update Matching Chapter in Developer Documentation

The priority of xmi:ids and attribute ids was swapped in Bug 457652.
Updates the matching chapter of the developer documentation to properly
specify the current default matching behavior. 

Signed-off-by: Stefan Dirix <sdirix@eclipsesource.com>
Change-Id: Iee333119d92c7db85783e6c5295ea7918683ff11
1 file changed