Improvements to CSV, WEBS transformers and adds Custom transformer

Added

• CsvToEs class added which imitates style of other XToEs classes for easier overriding / maintenance
• Custom formats now supported, although no functionality provided since the type of format cannot be predicted
• Adds documentation for custom format setup

Changed

• CSV to ES transformation no longer accepts default column names, but instead looks for columns matching ES fields to use
• FileType elasticsearch transform now has swappable component when reading XML-type files. Webscraping script altered to manipulate HTML instead of XML object type

Removed

• CSV to ES transformation used to automatically assume columns as ES fields, this functionality has been removed