Add unittest for module `pythonforandroid.archs`

Replaced one of the python2 travis builds with python3 arm64-v8a

Merge release-2019.06.06 to develop

This means that pypi renders the README correctly

Merge 2019.06.06.post0 hotfix: set long_description_content_type in setup.py

Improved release model documentation

bugfix: unpack for nonzip archives also needs to compare basename(dir)

Make sure the pythonpackage functions return an error when
someone attempts to do so anyway

Add unittest for module `pythonforandroid.distribution`

pythonpackage can't return build requirements for wheels, make it return an error if attempted

To fix freetype build for `openSUSE` and maybe other oses.

Note: It seems that there is a bug in `bzip2-devel` for debian and derivatives which are distributed without a `pkg-config` file, so when we compile freetype with a debian os (or derivative) we build it without bzip2 support, so we enforce to disable bzip2 support, because we know that freetype works fine without bzip2 support

Resolves: #1854

Add `--without-bzip2` to freetype's configure args

Fix locating system python when it's not in $PATH (weird but happens, apparently)

Because we make use of some mock methods in module `test_util` (eg: `mock.assert_called_once`) which were introduced in python 3.6, so if the system python of the test system is lower than 3.6, then the tox tests will fail

Verifying the number of calls we made to some functions:
  - test_folder_exist
  - test_delete

…ggestions

Reviewers suggestions are:
  - Remove forgotten debug code
  - `style code` change for `test_current_directory_exception`
  - add test `mock_shutil_rmtree.assert_not_called()` for `test_temp_directory`

Also changed some lines that shouldn't be split (because are pep8 friendly without breaking it in multiple lines)

- fix file litter of constraint.txt
- fix --private relative paths during build.py's setup.py install
- fix "" and "." not being recognized as folder by pythonpackage.py

…tage

Because we only need those dependencies for our `tox` tests so we may speed up a little the overall CI tests timings. We also remove all the other apt commands performed in `before_install` because we don't need it.

Note: in order to successfully pass the test `test_pythonpackage_basic.test_virtualenv`, we need to deactivate the system virtualenv
See also: travis-ci/travis-ci#8589

Try to be more clear in README about api levels & quickstart

Add unittest for `pythonforandroid.util` and...

Because we changed the git flow and now our main branch is `develop`

Make the tox jobs run in parallel &...

Fix various setup.py processing bugs

Because we introduce the legacy version of openssl to made it work `python2legacy`, but we recently removed `python2legacy`, so there is no point to maintain this changes.
Also:
  - we shortens some lines to be friendly with pep8
  - removed comment about ndk-r15c because our minimal ndk is r17c, so this comment is now pointless

Note: the python3crystax recipe make use of this legacy openssl libs, but, as far as I know, nobody is maintaining the python3crystax recipe (probably is broken and we should remove it)

Remove legacy version of openssl

Fix wrong env variable for `hostpython build path` in `archs.py`

fix ctypes-util-find-library issue for python2

permisssion => permission

Typo

Add unittest for module `pythonforandroid.bootstrap`

Fix `run_pymodules_install` when `project_dir` isn't supplied

Undid unnecessary parts of 1.16.4 recipe change

Fully replaced numpy 1.15.1 patches with 1.16.4 patches

Removed git commit info from patches

Regression test for the fix introduced in #1898.

#1900 logs failure

…ules_install_regression_test

Simple run_pymodules_install test, refs #1898

Updated numpy recipe to version 1.16.4