Command provider aliases

[cvarela]

Incorporate aliases of the different strategies to choose the commands to be executed:

Current value	Aliases
com.dattack.dbping.engine.SqlCommandRandomProvider	random
com.dattack.dbping.engine.SqlCommandRoundRobinProvider	round robin, round-robin, roundrobin
com.dattack.dbping.engine.SqlCommandWeightedRandomProvider	weighted random, weighted-random, weightedrandom