Make dpservice-cli more like kubectl

[vlorinc]

• Create get aliases for following list functions (eg. get route now equals list routes):

listLoadbalancerPrefixes > (list lbprefixes = get lbprefix)
listLoadbalancerTargets > (list lbtargets = get lbtarget)
listPrefixes > (list prefixes = get prefix)
listRoutes > (list routes = get route)

• Following commands now don’t require additional parameters/flags (without parameter, they will list all available objects of their type):

get firewallrule
get virtualip
get nat
get interface
list lbprefixes
list prefixes

• List and get commands now support singular/plural aliases interchangeably (eg. get routes, list prefix)

Closes #26

[guvenc]

Thanks. Looks good to me.