webadmin: DataCenters main-tab: sub-tabs resizable columns

Sub-tabs under DataCenters main-tab now support
resizable columns.

* Invoked enableColumnResizing() on each sub-tab.
* Added a static width value for each column.

Change-Id: I71465d36e5c18ecb8eb6dbca436feaeea1c902a9
Signed-off-by: Daniel Erez <derez@redhat.com>