Rework 'lcores' and 'memory_channels' into a new 'dpdk_config'
subsection in an effort to make these attributes SUT specific; the
traffic generator, more often than not, does not need this information.
Ideally, if such information is needed, then it will be listed in the
'traffic_generator' component in TG Node configuration. Such logic is
not introduced in this patch, but the framework can be rewritten to do
so without any implications of extreme effort.

To make this work, use_first_core has been removed from the framework
entirely in favor of doing this within the LogicalCoreListFilter object.
Since use_first_core was only ever activated when logical core 0 was
explicitly defined, core 0 can be removed from the list of total logical
cores assuming that it was not listed within filter_specifier.

This patch also removes 'vdevs' from 'system_under_test_node' and moves
it into 'executions.'

Bugzilla ID: 1360
Signed-off-by: Nicholas Pratte <npratte@iol.unh.edu>

-    memory_channels: 4 # tells DPDK to use 4 memory channels
-    hugepages_2mb: # optional; if removed, will use system hugepage configuration
-        number_of: 256
-        force_first_numa: false