backport 997b7b18

SVM sigmoid kernel fix (issue #13621) (#13718)

* Added test for sigmoid case for retrieving support vectors

* undo unhelpful test

* add test for sigmoid SVM with data that is easily separable into two concentric circles

* Update sigmoid kernel to use tanh(gamma * <x, y> + coef0) instead of -tanh(gamma * <x, y> + coef0)

* remove unnecessary constraint on coef0

* cleanup

* fixing inappropriate use of doubles

* Add f to float literal

* replace CV_Assert with ASSERT_EQ where appropriate

Found via `codespell -q 3 -I ../opencv-whitelist.txt --skip="./3rdparty"`

Found via `codespell`

* export SVM::trainAuto to python #7224

* workaround for ABI compatibility of SVM::trainAuto

* add parameter comments to new SVM::trainAuto function

* Export ParamGrid member variables

Added a writeFormat() method to Algorithm which must be called by the
write() method of derived classes.

related to issue 4969
fixes issue 5891
fixes issue 5922

Someone forgot to wrap the load function for SVMs in the
corresponding ml python module. Fixed that.

applying patch by rxtsolar: https://github.com/Itseez/opencv/pull/5422 for the master branch (even though it's actually not that important here)

add smoke test

(cherry picked from commit 3a1bb933)

Fix SVM::trainAuto (Bug #4464)

commit 5c379aa1
Merge: e800800b 3646967d
Author: Сергей Нужный <snuzhny@stc-spb.ru>
Date:   Wed Apr 8 12:44:46 2015 +0300

    Merge branch 'master' of https://github.com/Nuzhny007/opencv

commit e800800b
Author: Сергей Нужный <snuzhny@stc-spb.ru>
Date:   Wed Apr 8 12:43:38 2015 +0300

    Squashed commit of the following:

    commit 3646967d
    Author: Сергей Нужный <snuzhny@stc-spb.ru>
    Date:   Tue Apr 7 15:48:30 2015 +0300

        Fix bug in SVM::trainAuto

    commit 0c24ccf5
    Author: Сергей Нужный <snuzhny@stc-spb.ru>
    Date:   Tue Apr 7 15:43:59 2015 +0300

        Revert "Fix bug in SVM::trainAuto"

        This reverts commit 225da022.

    commit 225da022
    Author: Сергей Нужный <snuzhny@stc-spb.ru>
    Date:   Tue Apr 7 15:09:47 2015 +0300

        Fix bug in SVM::trainAuto

commit 3646967d
Author: Сергей Нужный <snuzhny@stc-spb.ru>
Date:   Tue Apr 7 15:48:30 2015 +0300

    Fix bug in SVM::trainAuto

commit 0c24ccf5
Author: Сергей Нужный <snuzhny@stc-spb.ru>
Date:   Tue Apr 7 15:43:59 2015 +0300

    Revert "Fix bug in SVM::trainAuto"

    This reverts commit 225da022.

commit 225da022
Author: Сергей Нужный <snuzhny@stc-spb.ru>
Date:   Tue Apr 7 15:09:47 2015 +0300

    Fix bug in SVM::trainAuto

commit 3646967d
Author: Сергей Нужный <snuzhny@stc-spb.ru>
Date:   Tue Apr 7 15:48:30 2015 +0300

    Fix bug in SVM::trainAuto

commit 0c24ccf5
Author: Сергей Нужный <snuzhny@stc-spb.ru>
Date:   Tue Apr 7 15:43:59 2015 +0300

    Revert "Fix bug in SVM::trainAuto"

    This reverts commit 225da022.

commit 225da022
Author: Сергей Нужный <snuzhny@stc-spb.ru>
Date:   Tue Apr 7 15:09:47 2015 +0300

    Fix bug in SVM::trainAuto

2. Algorithm::load/save added (moved from StatModel)
3. copyrights updated; added copyright/licensing info for ffmpeg
4. some warnings from Xcode 6.x are fixed

This reverts commit 225da022.

- added test for loading legacy files
- added version to new written models
- fixed loading of several fields in some models
- added generation of new fields from old data

initial commit; ml has been refactored; it compiles and the tests run well; some other modules, apps and samples do not compile; to be fixed