Fix get_index_root_data() to work with out-of-order trains in files

See merge request !16

Add lit frame selection

See merge request !14

Drop empty trains before reading in parallel with pasha

See merge request !13

Only touch sources when operations are properly handled

See merge request !12

Fix returning no mask when XTDF slicing is enabled but entire train selected

See merge request !11

Properly copy attributes of CONTROL key leafs and RUN-only keys

See merge request !9

Initial performance optimizations for frame selection pilots

See merge request !8

Add verbose profiling to debug logging

See merge request !7

Simplify reduction operation implementations and error handling

See merge request !6

Support additional and maintain existing data compression

See merge request !3

Support select-entries and select-xtdf operations

See merge request !2