Lemoncheesecake

- **HTML report**: fix regression introduced in the previous 0.19.6 version where raw attachments are displayed
as images and vice versa

- **API & HTML report**: three new `lemoncheesecake.api` functions are available: `prepare_image_attachment`,
`save_image_file` and `save_image_content` that allow to save an image as attachment in the report and to
display the image inline in the HTML report

API breaking changes

- **API**: the `setup_test` and `teardown_test` suite methods now take the test instance as argument instead
of the test name
- **API**: the `teardown_test` suite method now takes a second argument that represents the status of the test "so far"

- **cli**: fix broken `--from-report` argument handling (regression introduced in 0.19.4)

- **reporting**: fix unordered tests in suite when test's status is disabled or skipped
- **reporting**: fix unordered top suites
- **matchers**: has_item: in matcher details, display the index of the matching element instead of the sub matcher
details

- **API**: the `MatchResult` class now implements `__bool__` (and `__nonzero__`) method and then can be used in boolean operations
- **API**: the `check_that`, `require_that`, `assert_that` functions now return a `MatchResult` instance (instead of a boolean for
the `check_that` and no return value for the two other functions)
- **API**: the `check_that_in`, `require_that_in`, `assert_that_in` functions now return a list of matcher results
- **API**: the `has_item` matcher now returns an enhanced match result instance with `index` (of the matched item in
the actual list) and `item` attributes

- **junit**: fix for multi-threads run