MO dev guide refactoring (#3266) (#3595)

* Release mo dev guide refactoring (#3266)

* Updated MO extension guide

* Minor change and adding svg images

* Added additional information about operation extractors. Fixed links and markdown issues

* Added missing file with information about Caffe Python layers and image for MO transformations dependencies graph

* Added section with common graph transformations attributes and diagram with anchor transformations. Added list of available front phase transformations

* Added description of front-phase transformations except the scope-defined and points defined. Removed legacy document and examples for such transformations.

* Added sections about node name pattern defined front phase transformations. Copy-pasted the old one for the points defined front transformation

* Added description of the rest of front transformations and and all middle and back phase transformations

* Refactored Legacy_Mode_for_Caffe_Custom_Layers and updated the Customize_Model_Optimizer with information about extractors order

* Added TOC for the MO Dev guide document and updated SVG images with PNG ones

* Fixed broken link. Removed redundant image

* Fixed broken links

* Added information about attributes 'run_not_recursively', 'force_clean_up' and 'force_shape_inference' of the transformation

* Code review comments

* Added a section about `Port`s

* Extended Ports description with examples

* Added information about Connections

* Updated MO README.md and removed a lot of redundant and misleading information

* Updates to the Customize_Model_Optimizer.md

* More updates to the Customize_Model_Optimizer.md

* Final updates for the Customize_Model_Optimizer.md

* Fixed some broken links

* More fixed links

* Refactored Custom Layers Guide: removed legacy and incorrect text, added up-to-date.

* Draft implementation of the Custom layer guide example for the MO part

* Fixed broken links using #. Change layer->operation in extensibility documents

* Updated Custom operation guide with IE part

* Fixed broken links and minor updates to the Custom Operations Guide

* Updating links

* Layer->Operation

* Moved FFTOp implementation to the template extension

* Update the CMake for template_extension to build the FFT op conditionally

* Fixed template extension compilation

* Fixed CMake for template extension

* Fixed broken snippet

* Added mri_demo script and updated documentation

* One more compilation error fix

* Added missing header for a demo file

* Added reference to OpenCV

* Fixed unit test for the template extension

* Fixed typos in the template extension

* Fixed compilation of template extension for case when ONNX importer is disabled

Co-authored-by: Alexander Zhogov <alexander.zhogov@intel.com>

docs/HOWTO/mo_extensions/ops/FFT.py

@@ -0,0 +1,40 @@
+"""
+ Copyright (C) 2018-2020 Intel Corporation
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+      http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+"""
+
+#! [fft:operation]
+from mo.front.common.partial_infer.elemental import copy_shape_infer
+from mo.graph.graph import Node, Graph
+from mo.ops.op import Op
+
+
+class FFT(Op):
+    op = 'FFT'
+    enabled = False
+
+    def __init__(self, graph: Graph, attrs: dict):
+        super().__init__(graph, {
+            'type': self.op,
+            'op': self.op,
+            'version': 'custom_opset',
+            'inverse': None,
+            'in_ports_count': 1,
+            'out_ports_count': 1,
+            'infer': copy_shape_infer
+        }, attrs)
+
+    def backend_attrs(self):
+        return ['inverse']
+#! [fft:operation]