Always have a TargetPhraseCollection.

Before:
Name:moses_chart        VmPeak:12027904 kB      VmRSS:10151884 kB       real:173.000
real    2m53.608s
user    2m44.003s
sys     0m8.401s

After:
Name:moses_chart        VmPeak:11988700 kB      VmRSS:10112684 kB       real:177.500
real    2m58.393s
user    2m39.673s
sys     0m12.171s
In-line PhraseDictionaryNodeMemory with the hash table data structure

Before:
Name:moses_chart        VmPeak:11988700 kB      VmRSS:10112684 kB
real    2m58.393s
user    2m39.673s
sys     0m12.171s

After:
Name:moses_chart        VmPeak:11952688 kB      VmRSS:10077304 kB
real    2m42.329s
user    2m31.219s
sys     0m10.261s