* [FRONTEND][TFLITE] Add support for TFLite_Detection_PostProcess

This adds support for the custom operator
TFLite_Detection_PostProcess which is commonly used in
object detection networks such as SSD Mobilenet. It
only adds support for when use_regular_nms = False.

Change-Id: I819b253c0eb6f0fa55da65d2634e09359b888828

* Added a test for the tflite custom op

Change-Id: Ie5baa092deae9a8bcffd2ebd9f6d346b90e58afd

* Removed trailing comma

Change-Id: Ib08f02b5f1a59a883048bfb36e4321152cd2e7f2

* Added spaces between divide

Change-Id: If1171fc03d211a809cedeb800804394972af4060

* Formatted comment

Change-Id: I3ce7e69b8d2c73aec57369c1c64ea1eec07f087b

* Reduced line length in test

Change-Id: I49eaafc3369070f8f3e85fbb965ad20972096c68

* Set random seed for test

Change-Id: I542a787d11422ea83c52147b2cb1144fcef0dd77

* Fixes to style

Change-Id: I2971b8ecebe08c882b2481a99f67cfbe515e0b1f

* Assert for incorrect number of inputs

Change-Id: I393f3b3b62be73e427498d98456fb1d5a214e0af

* Change comparison to pass linting

The linter was updated, so I needed to fix
a small style issue as a result.

Change-Id: Ia3c954565a00de92e7fb1912eae9ed9875d60c7c