Don't mention `inspect` and `IO.inspect` in IEx.Options

Those function do not query `IEx.Options.get :inspect` by default
Add @doc false to each gen* callback by default
Start refactoring LocalsTracker to support more vertices
Extract imports handling to locals tracker (soon to be renamed)
Use precalculated binary size
Rename Kernel.LocalsTracker to Module.DispatchTracker
Record each definition on tracker as soon as defined
Check for imports conflicts in batches
Ensure warnings are proper with yanked and reattached overridables
Don't mention the project owner, this is open source
Update pull request creation guidelines
Be more strict about changes in master
"Thank you" sounds better
Merge pull request #1120 from alco/contributing-guidelines

Contributing guidelines
Module.DispatchTracker also records remotes
Provide source information to all dispatches and complement the API
Update mailing list links
development and questions
Ensure aliases from macros are properly expanded, closes #1123