Refrapt

This release adds a new feature, Clean mode, which can be enabled via the Command Line option `--clean`. This will skip the normal processing, and evaluate the existing mirror stored on the machine, and clean up old files that aren't necessary.
This allows for running Refrapt as a cronjob in order to only clean mirrors.

Issues addressed in this release:
1. Add Clean Mode at request of 17
2. Fix bug identified in 18

Adds a new option to the Configuration file called `disableClean` which when set to True will skip the cleaning process entirely, rather than requiring that the clean option is disabled for each individual mirror.

Goes towards 17.

As described in 16, the Refrapt host should be able to download Translation indexes for multiple languages, to support a multi-language client base.

Multiple Languages can now be added to the Configuration file.

Addresses an issue raised in 15 due to an incorrect Regex expression not accounting for .diff files in Source repositories.

Fixes an issue identified in 14 when processing a src repository.

Optimise Index downloads by reading the "Release" file for candidate files.

Additionally Linting has also been performed.