add 3 new test cases for SelectCoins()
add 3 new test cases for SelectCoins()

1. More coins should be selected when effective fee < long term fee.
2. Less coin should be selected when effective fee > long term fee.
3. If a coin is preselected, it should be selected even if disadvantageous.

namecoin/namecore,bitcoinsSG/bitcoin,tecnovert/particl-core,namecoin/namecoin-core,particl/particl-core,lateminer/bitcoin,fujicoin/fujicoin,bitcoin/bitcoin,Xekyo/bitcoin,instagibbs/bitcoin,tecnovert/particl-core,fanquake/bitcoin,bitcoin/bitcoin,kallewoof/bitcoin,namecoin/namecoin-core,ajtowns/bitcoin,mruddy/bitcoin,domob1812/bitcoin,ajtowns/bitcoin,AkioNak/bitcoin,GroestlCoin/GroestlCoin,AkioNak/bitcoin,sipsorcery/bitcoin,jamesob/bitcoin,fanquake/bitcoin,bitcoin/bitcoin,bitcoin/bitcoin,lateminer/bitcoin,jambolo/bitcoin,GroestlCoin/GroestlCoin,namecoin/namecore,bitcoinsSG/bitcoin,sipsorcery/bitcoin,kallewoof/bitcoin,namecoin/namecoin-core,jambolo/bitcoin,jamesob/bitcoin,kallewoof/bitcoin,jamesob/bitcoin,bitcoinsSG/bitcoin,mruddy/bitcoin,tecnovert/particl-core,sstone/bitcoin,fujicoin/fujicoin,jamesob/bitcoin,fanquake/bitcoin,instagibbs/bitcoin,jambolo/bitcoin,bitcoinsSG/bitcoin,jambolo/bitcoin,AkioNak/bitcoin,namecoin/namecoin-core,sstone/bitcoin,GroestlCoin/GroestlCoin,sipsorcery/bitcoin,andreaskern/bitcoin,jamesob/bitcoin,fanquake/bitcoin,sipsorcery/bitcoin,instagibbs/bitcoin,ajtowns/bitcoin,fujicoin/fujicoin,tecnovert/particl-core,particl/particl-core,GroestlCoin/bitcoin,lateminer/bitcoin,mruddy/bitcoin,instagibbs/bitcoin,andreaskern/bitcoin,fujicoin/fujicoin,GroestlCoin/GroestlCoin,Xekyo/bitcoin,sipsorcery/bitcoin,namecoin/namecore,GroestlCoin/GroestlCoin,namecoin/namecore,namecoin/namecoin-core,sstone/bitcoin,instagibbs/bitcoin,domob1812/bitcoin,domob1812/bitcoin,domob1812/bitcoin,mruddy/bitcoin,bitcoin/bitcoin,GroestlCoin/bitcoin,sstone/bitcoin,sstone/bitcoin,bitcoinsSG/bitcoin,Xekyo/bitcoin,particl/particl-core,kallewoof/bitcoin,jambolo/bitcoin,fanquake/bitcoin,fujicoin/fujicoin,AkioNak/bitcoin,AkioNak/bitcoin,ajtowns/bitcoin,lateminer/bitcoin,sstone/bitcoin,andreaskern/bitcoin,jamesob/bitcoin,ajtowns/bitcoin,domob1812/bitcoin,particl/particl-core,particl/particl-core,tecnovert/particl-core,sipsorcery/bitcoin,lateminer/bitcoin,GroestlCoin/bitcoin,andreaskern/bitcoin,fujicoin/fujicoin,andreaskern/bitcoin,bitcoinsSG/bitcoin,GroestlCoin/GroestlCoin,mruddy/bitcoin,Xekyo/bitcoin,domob1812/bitcoin,GroestlCoin/bitcoin,tecnovert/particl-core,ajtowns/bitcoin,AkioNak/bitcoin,instagibbs/bitcoin,lateminer/bitcoin,GroestlCoin/bitcoin,mruddy/bitcoin,Xekyo/bitcoin,namecoin/namecore,fanquake/bitcoin,kallewoof/bitcoin,andreaskern/bitcoin,jambolo/bitcoin,namecoin/namecore,namecoin/namecoin-core,bitcoin/bitcoin,GroestlCoin/bitcoin,kallewoof/bitcoin,particl/particl-core,Xekyo/bitcoin