Enhance user-friendness and clean code

[lubynets]

Major changes:

1. Enabled writing the QA output to already existing file (use Task::SetOutputFileName(fileName, "update") function) - useful when the QA consists of several different QA::Tasks taking as an input different file lists, but the output should be written into the same file.
2. Made flexible using custom or entry-driven naming of output TDirectory:

• output TDirectory name is equal to EntryConfig's name - default;
• output TDirectory name is set by user - use Task::SetTopLevelDirName(dirname, false) or just Task::SetTopLevelDirName(dirname) function;
• output TDirectory name is set by user and then appended with EntryConfig's name - use Task::SetTopLevelDirName(dirname, true) function.
  For more details see the PR where Task::SetOutputFileName() was initially introduced.

Minor changes:
Removed obsolete scripts and macros.