--update show-pstats script after transpose of wrsPstats into wrsPstatsTable
--update wrs-user-manual with information about possible usage of snmptable

Instead of using script show-pstats, snmptable can be used. For example:
snmptable -c public -v 2c switch_IP -m all -M $WRS_OUTPUT_DIR/build/buildroot-2011.11/output/build/netsnmp-5.6.1.1/mibs/:userspace/snmpd/ WR-SWITCH-MIB::wrsPstatsTable
Signed-off-by: Adam Wujek <adam.wujek@cern.ch>