EFTFitter framework to perform chi2 tests on EFT templates

Requirements
- C++17 compiler or later
- ROOT6
- original development and production were done under C++14 gcc 6.2.0 and ROOT 6.12/04 and 6.14/00
- current version bumped to C++17 gcc 10.1.0 and 6.24/00, future development will happen only on this or later standard

Notes
- execution is based on putting together an execution macro and compiling it with the source
- file exec/example_fit.cc is provided showing how such an execution macro looks like
- file exec/execMacro.sh is provided to ease compiling and running the macro
- more details in exec/example_fit.cc
- also exec/example_hybrid.cc for hybrid mode usage

To-do (in no particular order)
- address in-code FIXMEs
- generally more flexible workflow
- saving of computed chi2 into trees
- also of confidence intervals (in general such that the point computation can be split into multiple jobs)
- marginal uncertainties for 2 and higher op cases
- more clever way of chi2 minimization; brute force doesn't scale up with nOp > 1
- settings related to file saving

Feedback and/or bug report are welcome
Updated	08/03/2023