Ability for httpsync script to compare file list files

[Rexus]

Rsync is able to make use of file list files provided at the mirrors. This enables an easier check with less calls on source but also assumes that the file list is correct with reality.

The httpsync script lacks this feature and would benefit for an easier approach when mirrors containing such files is available.
The following features are to be added to the httpsync script:

• New argument for providing a filelistfile
• Compare the file between source and destination, extract a list of files to be added or removed ad destination
• Keep the exclude query matches based on paths

The following to be done to the main script:

• Add the checkresult status from httpsync just like rsync has

[Rexus]

The scope for how advance this should be is lower. A simple check whether the files are equal or not is sufficiant. Does not need to be via the httpsync script