Fix broken Install tests

Fixtures were initially not used because Adios supports CMake 3.6,
which did not yet have fixtures (they were introduced in 3.7.)
However, adding the fixtures can be done in a backwards compatible
manner without affecting pre-3.7 builds. Add test fixtures to ensure
that Install.Setup always gets run before the other Install tests, even
if it's not specified in the CTest -R regex. (Note that we are still
using the DEPENDS property in addition to FIXTURES_REQUIRED in order
to support 3.6.)

* release:

* commit 'd93747d5':
  remove debug prints in BP4 serializer
  Fix flake8 errors
  Install all .py files for bp4dbg
  bp4dbg: dump metadata too. Print values for characteristics and attributes. Fix: BP4 and BP3 attribute length in data was written as 8 bytes and the wrong value; now writing the correct length and on 4 bytes only.

* release:

  Disable install tests until CI issues are resolved

Disable install tests until CI issues are resolved

Bp4dbg

bp4dbg: dump metadata too. Print values for characteristics and attributes. Fix: BP4 and BP3 attribute length in data was written as 8 bytes and the wrong value; now writing the correct length and on 4 bytes only.

* release:

  Add Install tests
  Skip first argument when generating config file
  Make CMAKE_INSTALL_PREFIX configurable at install-time

Add Install tests

* release:

  MPI Barrier
  Modifying name
  VS error
  Fix aelocal array bug
  Update block count

Local array read block bug

* release:

  remove spurious printf

remove spurious printf

* release:

  Add the null transport
  Add the NullCore engine

* release:

  Take William's code review advice; make docs consistent with CMakeLists.txt
  Improvements to installation documentation.

* release:

  Fix VMD] tag encoding for string variables and dump strings correctly in bp4dbg
  Fix BP4Base::ResizeBuffer() to use vector size() not capacity() just like as it was fixed in BP3Base already
  Dump index table and fix flex8 errors
  Add a python tool bp4dbg to dump a BP4 dataset. Only for data files yet, not for metadata and index table.
  BP4 format changes in data.* files - Add tags to different elements in BP4 Data buffer   - [PGI...PGI] for PG blocks,   - [VMD..VMD] for variable metadata, data blocks are outside this tag   - [AMD..AMD] for attribute metadata, values are inside this tag - Pad variable metadata blocks so that variable data always starts on aligned position in memory (not on final file offset). - Do not write dimensions in characteristics in the data buffer since a fixed entry exists for dimensions. In ADIOS 1.x these could be different (variable ID vs actual dimension numbers) but ADIOS2 does not have this anymore. - Do not write footer (metadata) to the end of data file on close. Metadata only exists in the global md.0 file and inside the data buffers in data.* interspersed witht the data itself (for recovery) - Bug fix: use BP4Base::ResizeBuffer consistently instead of BufferSTL::Resize because they work differently based on capacity versus size. This fixes the CI test errors.

* release:

  fixed a few problems in ssc tests

Add a Null2 engine that operates at the core::Engine level

Improvements to installation documentation.

Bp4 buffer tags and bp4dbg.py tool

Updating count in BP3 and BP4 deserializer
Added test

fixed a few problems in ssc tests