clear_table_cache before each rename_column

Fixing issue https://github.com/rails-sqlserver/activerecord-sqlserver-adapter/issues/237

Not sure if this is the optimal solution, but it should work.
ignore rubymine-generated files
bugfix
Merge pull request #246 from michelgrootjans/master

Fixes issue 237: "No such column" when renaming some columns in the migrations