Now all header sections are parsed fully before returning
to read data sections.

Broken - this is a work in progress.

- test_open_file.py::test_open_incorrect_filename - UnboundLocalError:
  local variable 'file_obj' referenced before assignment
  fix: assign file_obj as empty string before usage.
- test_read.py::test_v12_inf_uwi_leading_zero_value -
  lasio.exceptions.LASHeaderError: Line 18 (section ~P): "~C"
  fix: stop parsing section when we are at a new section.

Fix 2 test failures

Change the leading zero test files to be sample*.las plus the leading
zero special case.  Previously the leading zero test files had other
special cases in them that caused their tests to exercise unrelated code
paths.

…section-test

Rearrange-Reader Branch: Fix test_read::missing-a-section test

Rearrange-Reader: Base leading zero test files on sample.las

- Add tests/examples/3.0 dir.
- Add the CWLS's 3.0 example las file.
- Copy the example file to sample_3.0.las to standardize with
  1.2 and 2.0 sample las files.
- Create a tests/test_read_30.py with basic read test.
  However, the test is set to SKIP because it current fails on the
  rearrange-reader branch

…30-test

To rearrange-reader branch: add basic las 30 test

This enables tests/test_read.py::test_barebones_missing_all_sections
to pass, but may not be the complete or final solution.

…test

To rearrange-reader branch:  fix barebones test

LAS 3.0 : Rearrange reader branch: Fix find_sections_in_file with text stream

The current tests check 1.2 version files with unknown sections.

Rearrange-Reader: Enable Unknown section tests to pass

- fixes tests/test_null_policy.py::test_null_policy_NULL_none

Rearrange Reader:  fix json and write tests

Merge to Rearrange-Reader: Add check if null should be replaced with nan

Parsing a data line with regexp_subs fixes common errors in the data
(~A) section. Adding the regexp_subs to inspect_data_section() fixes
the following tests by standardizing the line data resulting in
consistent date array lengths:
- test_null_policy_runon_replaced_1
- test_null_policy_runon_replaced_2
- test_null_policy_runon_ok_1
- test_null_policy_runon_ok_2
- test_write_sect_widths_12

To Rearrange-Reader branch: Fix 5 tests : calculating number of data columns