Remove LIBISF Support

This MR removes LIBISF support, which has been depreciated since 2020, and should have been removed in the 2021 release (version 10?).

Please let me know if I've missed anything in the build system.

Also tagging @micael.oliveira so he clocks the change.

Changes

• Removed redundant change log files
• Removed flags and IFDEFs for LIBISF
• Removed pdf presentations from the code documentation - they should not be carried with the source code
• Removed libYAML from external_libs