fix failed onnx tests

Context

This MR is intended to fix the failed onnx tests encountered in issue #50 (closed) and issue #46.

This includes the following problems:

• And/Equal: A mistake was made, the operator Equal was named And.
• AvgPooling: unsupported attrs dilations and ceil_mode
• MaxPooling: unsupported attr dilations

Detailed major modifications

The following modifications were made:

• Add Equal import/export
• Add dilations attr to Maxpooling
• Add dilations and ceil_mode to AvgPooling

TODO

This MR would only fix the following:

• Add Equal Op
• AvgPooling: add dilations, ceil_mode attrs
• MaxPooling: add dilationsattr