subscan splitting with known subscan size

scripts/split_bliss_scan.py

src/est/core/io.py

src/est/core/monotonic.py

src/est/core/process/split.py

src/est/core/sections.py

src/est/core/split_monotonic.py

src/est/gui/xas_object_definition/dialog.py

src/est/gui/xas_object_definition/hdf5.py

src/est/io/concatenated.py

src/est/io/information.py

src/est/tests/test_monotonic.py

src/est/tests/test_split_monotonic.py

src/orangecontrib/est/widgets/utils/xas_input.py