Move the standalone_edcu code to its own directory

src/epics/CMakeLists.txt

src/epics/edcu/CMakeLists.txt

src/epics/edcu/gps.hh

src/epics/edcu/standalone_edcu.cc

src/epics/edcu/test/daqdrc_standalone_edc_live_test

src/epics/edcu/test/epics_test.py

src/epics/edcu/test/test_standalone_edc_live_nds.sh.in

src/epics/seq/CMakeLists.txt