unused variables were commented out
updatedd .gitignore
Merge branch 'master' of github.com:TakashiSasaki/ns3-abe

Conflicts:
	.gitignore
Merge branch 'EunetSwitch'
updated .gitignore
OutputFileStream for logging
DifsWifiMacTest as simulation class
mobility settings were moved to ConstantMobilityNodeContainer class
MAC and PHY preparations were moved to WifiNodeContainer class
getNetDeviceContainer and getDevice in ConstantMobilityNodeContainer
SetReceiveOkCallback on YansWifiPhy
difs-wifi-mac uses companion classes
SetReceiveErrorCallback for YasnWifiPhy
reformatting
separating IPv4 related features to Ipv4NodeContainer class
factorial is a sample of tail recursion
IPv4 related methods were moved to Ipv4NodeContainer class
fixed signed and unsigned mismatches
scheduleSendPacket accepts destination node
some assertions were inserted