Modularise S3 protocol

Add a protocol interface to abstract the s3 implementation away from the server. The server handlers now call generic protocol functions on objects created in a protocol factory. Only this factory knows, that the underlying objects are S3.

ChangeLog:
* add virtual classes for protocols
* move s3 specific implementations to own folder/namespace and inherit generic protocol
* add protocol_factory to generate s3 objects for the server
* move fifo and phobos implementations to own namespace to mirror the same layout as for the protocol
6 jobs for modularise-http-interface in 16 minutes and 50 seconds (queued for 3 seconds)
Status Name Job ID Coverage
  Static Analysis
passed Format #6943
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00:00:34

passed Lint #6944
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  Build
passed Documentation #6945
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  Test
passed Authorisation Disabled #6947
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00:02:55

passed Centos7 #6948
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00:02:17

passed Default #6946
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00:02:47