Update Gemfile since group assets doesn't exist anymore in Gemfile
removes activerecord/examples/associations.png

This seems to be a legacy file, I cannot find any place where it is used.
removes bindir from the rails gemspec

Nowadays the rails gem itself has no executables.
Extract Firebird database tasks.
Extract Sqlserver database tasks.
Extract Oracle database tasks.
Add deprecation message on Firebird / Sqlserver / Oracle database tasks.
Fix wrong method name.
Change method order for consistency.