Removed operator=(char) from TStr as it was nice place for making bugs (e.g. TStr a; a = 0;)
Removed TStr(char, char) as nobody used it. TStr(char) was fixed so that in case char==0, it creates empty string.
Merge pull request #119 from blazf/TStr

Reverting parts of API, removed some dangerous constructors and operator= in TStr.