HFInvMassFitter-1.0

HFInvMassFitter is set up to work standalone and refactored:

• obsolete headers, variables and pieces of code removed;
• use TH1 instead of TH1F to be more general with possible input histogram type;
• more safe type castings employed (e.g. avoid reinterpret_cast and use Get<TH1>() instead of Get() before static_cast);
• instances from the standard library (string, vector, cout) prepended with std::;
• removed using directive from header;
• the code is made less D0-hardcoded;
• fixed typos in comments and variable names

Generalized the slicing variable - before it was Pt only, but now it is settable via config (useful for e.g. lifetime slicing).