Rails 4.2 Handle NUMBER sql_type as `Type::Integer` cast type

This pull request  handles NUMBER sql_type as `Type::Integer` cast type since Oracle database NUMBER datatype handles interger and decimal.

Then this pull request fixes following failures since this commit has been merged.
https://github.com/rails/rails/commit/6b2ff4fa2082a51915d1c3e526b9194df44682de

```ruby
ARCONN=oracle ruby -Itest test/cases/core_test.rb -n test_inspect_class
 
ARCONN=oracle ruby -Itest test/cases/migration/change_schema_test.rb -n test_column_exists_with_definition
 
ARCONN=oracle ruby -Itest test/cases/migration/columns_test.rb -n test_change_column
 
ARCONN=oracle ruby -Itest test/cases/migration/references_statements_test.rb -n test_add_belongs_to_alias
 
ARCONN=oracle ruby -Itest test/cases/migration/references_statements_test.rb -n test_creates_reference_id_column
 
ARCONN=oracle ruby -Itest test/cases/reflection_test.rb -n test_integer_columns
 
ARCONN=oracle ruby -Itest test/cases/view_test.rb -n test_column_definitions
 
ARCONN=oracle ruby -Itest test/cases/view_test.rb -n test_column_definitions
 
ARCONN=oracle ruby -Itest test/cases/xml_serialization_test.rb -n test_to_xml
```
This commit creates a regression, I'm not sure if we can fix it since Oracle NUMBER
datatype can handle integer and decimal.

```ruby
ARCONN=oracle ruby -Itest test/cases/connection_adapters/type_lookup_test.rb -n test_decimal_without_scale
```