test: extract unitutil.mock and unitutil.file
test: transplant tests.unitutil.cxml
test: refactor test_section to use cxml
test: refactor oxml.parts.test_document to cxml
test: refactor oxml.test_text.py to use cxml
test: refactor parts.test_document.py to use cxml
test: refactor tests.test_text to use cxml
test: refactor tests.test_section to use cxml
test: refactor tests.test_shape to use cxml
test: refactor tests.test_table to use cxml