Create and use testing module, remove builder tests, clean up test code

[rly]

• Add backwards compatibility tests for reading basic files generated using PyNWB 1.0.2, 1.0.3, and 1.1.0. More tests should be added. Note that files generated using earlier versions of PyNWB do not validate because of the change of experimenters and related_publications being string to tuple/list in the current schema. The validator needs to validate against the schema version used to generate the file. See validator erroneously catches non-vector experimenter and related_publications #1090.
• Expose and use hdmf.testing.TestCase as pynwb.testing.TestCase in src/testing/testmap.py. Add TestMapNWBContainer and TestMapRoundTrip and TestDataInterfaceIO under pynwb.testing.TestCase. This eliminates the need for tests/integration/ui_write/base.py
• If a string is passed in for NWBFile.experimenter or NWBFile.related_publications, automatically make it a tuple.
• Remove builder tests, which are inconsistent and difficult to maintain
• Move tests/unit/test_core_NWBContainer.py to tests/unit/test_core.py
• Remove some Python 2.7 specific code
• Remove old dead code, e.g., tests/build_fake_data.py and tests/build_fake_extension.py

Changes require the latest HDMF.

[codecov]

Codecov Report

Merging #1117 into dev will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##              dev    #1117   +/-   ##
=======================================
  Coverage   68.09%   68.09%           
=======================================
  Files          37       37           
  Lines        2282     2282           
  Branches      398      398           
=======================================
  Hits         1554     1554           
  Misses        659      659           
  Partials       69       69

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update da212af...2c0f687. Read the comment docs.