Implement possibility of handling of NUMBER columns as :float

Adds new `ActiveRecord::ConnectionAdapters::OracleEnhancedAdapter.number_datatype_coercion` class attribute preference

Makes change to handling of virtual NUMBER columns in schema dumps

Adds RSpec test for simulated db:schema:dump & db:test:load scenario amongst others.
Has some small cleanup & syntax improvement changes.

Disclaimer:
  This commit includes Benjamin Ortega's (github: substars) code from https://github.com/rsim/oracle-enhanced/pull/258

Closes: rsim/oracle-enhanced#258

Signed-off-by: Aleksandrs Ļedovskis <aleksandrs@ledovskis.lv>
Merge pull request #418 from aledovsky/bug/float_column_type

Implement handling of NUMBER columns as :float
Update the error message to support JDBC and OCI connections
Merge pull request #443 from yahonda/update_ora_1438

Update the error message to support JDBC and OCI connections
Tag bind params with a bind param object
Merge pull request #444 from yahonda/mod_substitute_at

Tag bind params with a bind param object
Initial support for adequeterecord branch
Dummy
Support `without_prepared_statements?` to handle `unprepared_statement` method
Merge pull request #447 from yahonda/support_without_prepared_statement

Support `without_prepared_statements?` to handle `unprepared_statement`
Merge remote branch 'upstream/master' into adequaterecord

Conflicts:
	lib/active_record/connection_adapters/oracle_enhanced_adapter.rb
Update history for v1.5.5
Merge pull request #448 from yahonda/prepare_v155

Update history for v1.5.5
Release 1.5.5
Create OracleEnhancedDatabaseStatements module
then extract some methods from oracle_enhanced_adapter.rb
into oracle_enhanced_database_statements.rb
Merge pull request #449 from yahonda/extract_database_statements

Create OracleEnhancedDatabaseStatements module
Merge remote branch 'upstream/master' into adequaterecord

Conflicts:
	lib/active_record/connection_adapters/oracle_enhanced_adapter.rb