Hydrogen import: move all notes from C2 to A4

### Enhancement Summary
Whenever a Hydrogen song is imported, all the steps in sequencer are by default at C2 (default value for Hydrogen). Enhancement: to move all notes 33 semitones upward so steps are by default at A4.

#### Justification
Hydrogen defaults the original sample to the C2 in drumkits. LMMS defaults original sample to A4 key. Importing a Hydrogen track (h2song) file and opening piano roll of any beat/bassline places notes at C2. When the track is replaced with sample sound we need to move notes from C2 to A4, effectively moving everything 33 semitones up (or moving the basenote 33 semitones down to C2) to make it sound like the original. This is a trouble, especially for files with lots of drum patterns.
It is possible to move master pitch up by 33, but then we need to disconnect it from each instrument we add subsequently.

See this screenshot:
(This is what I mean when I say Hydrogen defaults the sample basenote to C2)

Start by tracing the Hydrogen h2song import path into sequencer steps and compare the imported C2 placement with the piano-roll view. The work is done when imported Hydrogen notes appear at A4, equivalent to moving them 33 semitones upward, without requiring a manual master-pitch adjustment.

Written by the indexing model from the issue text.