Working dilution (T) - ? - Generate Tecan file

The process needs to generate a Tecan file. Probably similar to Sequencescape - https://github.com/sanger/sequencescape/blob/next_release/app/models/batch/tecan_behaviour.rb

It has been created a new module for generation of tecan files that makes use of a layout strategy (assigns wells from sources to destination), an output strategy (adds volume information to assigned layout) and a file generation process (builds in tecan .gwl format). These three phases can be substituted by different implementations.
In order to work, the module uses as inputs an array of sources and an instance of the destination.

It has been included in commit two unit tests and two testing files for them.