New concept of columns for version 2.0

[Tigrov]

Main changes:

• 1. Realize TypeColumn classes (IntegerColumn, StringColumn, etc)
  ColumnSchema classes for performance of typecasting #752
• 2. Realize ColumnFactory
• 3. Realize ColumnBuilder
  It also fixes Type blob is generated instead of binary Mysql 8.0 db-mysql#249
• 4. Add ColumnDefinitionBuilder::buildType() method to get full name of db type, e.g. varchar(20)
  Get DB type without size #695
• 5. Realize ColumnDefinitionBuilder
  Refactoring \Yiisoft\Db\QueryBuilder\AbstractQueryBuilder::getColumnType #599
• 6. Remove pk abstract type constants ColumnSchemaInterface::...pk use ColumnBuilder::...pk() instead
  problem with new migration 2.0.6 db-migration#6
• 7. Replace ColumnSchema::name() with immutable ColumnSchema::withName()
• 8. Remove ColumnSchema::precision() (use ColumnSchema::size() instead)
• 9. Rename ColumnSchema::allowNull() to ColumnSchema::notNull() to be compatible with old Column::notNull()
• 10. Add isUnique(), check() and reference() to ColumnSchema to be compatible with old Column class
• 11. Rename AbstractColumnSchema to Column (combine Column and ColumnSchema classes)

The changes will solve few issues and after related improvements it will solve few more issues.
It will allow customize typecasting for table column.