Add comments in class CBotString.
Change existing comments in class CBotString to be compliant with doxygen.
Add function "const char* CBotString::CStr() const".
Add null pointer check in function "const CBotString& CBotString::operator+=(const CBotString& str)"
Remove functions "CBotString CBotString::Mid(int nFirst, int nCount) const" and "CBotString CBotString::Mid(int nFirst) const" because they were doublons of function "CBotString CBotString::Mid(int nFirst, int lg) const"