Merge pull request #103 from rupnikj/TStr

assignment fix
multithreaded
Merge branch 'TStr' of https://github.com/qminer/qminer into TStr
empty string optimized
constructor with own fixed memory leak;
...
Merge branch 'TStr' of https://github.com/rupnikj/qminer into TStr
fixed SplitLeftOfRightOf