Partial update of the typing

[julienmarantes]

I added class attributes that were missing from the typing from the last version of mxgraph (cf: diff)

Changed some params that should be optionnal, to be optionnal.

Correced some params typing that should not be alowwed to be null.

Some indentation corrections.

[julienmarantes]

Just saw one of the last pull request on the null params : If null is specified as the id, then the id is automatically created.

I don't know if it's the normal behavior, but from my point of view passing null to a function for a specific behavior wouldn't be a good practice..

[lgleim]

I don't know if it's the normal behavior, but from my point of view passing null to a function for a specific behavior wouldn't be a good practice..

Please note that this repository only contains typings, not code. So any complaints about the code style should go to the upstream repository.

Also: Your pull request contains actual code, not typings. As such, I kindly ask you to review your pull request and remove the included implementation code to avoid conflicts.