Add Orthogonal initializer

[zaleslaw]

We are missing some initializers to fully support the export of models from Keras. One of them is the Orthogonal initializer.

Add an initializer class, write documentation for it, write a test for it, try, if possible, create a small trainable network with it (in your own GitHub) and attach a link.

Also, support for export and import of initializer in JSON format should be added (see ModelLoader.kt and ModelSaver.kt)

A detailed description of the initializer can be found here

[zaleslaw]

@therealansh, please leave a comment here, to assign this issue on you

[therealansh]

Oh sorry @zaleslaw ! Might have missed on this one. I'll be completing the tests soon and finalising the PR.

[zaleslaw]

Fixed in #84