Switch off httplib in minimal configuration
Summary:
MITK_USE_httplib is on by default which will in turn require OpenSSL, which should not be a requirement for minimal builds or build configurations deriving from Miminal.cmake like CoreCmdApps.cmake.
Fixes T30491.
Test Plan: Already tested with CoreCmdApps build on CentOS 7.
Reviewers: floca, O1 MITK Reviewer Group I
Reviewed By: floca, O1 MITK Reviewer Group I
Maniphest Tasks: T30491
Differential Revision: https://phabricator.mitk.org/D977