getRoot() semantics changed with ExtJS5.

To avoid further annoyances when ExtJS6 is around the corner, replace the call
to this private method, set rootProperty in the ObjectStore call,
and use the value of rootProperty to filter out the content of the server
answer.

This patch does the following:
 * remove the EXT5DEBUG header we added previously
 * build the items[] array as a one-dimensional array, as PVE.panel.Config
 with ExtJS5 is not able to find the elements otherwise
 * rename the problematic panel tabs with TODO suffix, to be dealed later on

Based on the JSSRC variable of the www/manager Makefile.
Files not yet commited to www/manager5 are commented out.