Apply good practices in the project

[lubynets]

Disclaimer: in the PR #136 there was added a header infra/HelperFunctions.hpp which contains some functions (either AnalysisTree-specific or plain ROOT / c++) used in analysis tasks. It should be admitted that the infra is not a proper place for such a header, while examples would fit better. The reason why the header is placed in infra is that these function are also useful for AnalysisTreeQA, which is not supposed to include headers from AnalysisTree/examples.
The mentioned header should not be included in any AnalysisTree / AnalysisTreeQA classes for the sake of generality (only at users' tasks) - so the infra/HelperFunctions.hpp can be (re)moved at any time.

• AnalysisTree classes are made independent on infra/HelperFunctions.hpp
• Improved weights application (explicitly foresee case of weights == 1)
• Got rid of compiler warnings, applied clang-formatting, followed clang-tidy suggestions
• Updated ClassDef version of Track and Particle classes (see details in Issue #146)