[TEST] FMIndex: tested more specs
[FIX] FMIndex: always initialize first sentinel positions to false during BWT construction
[FIX] FMIndex: initialize first indicator positions in CSA construction
Merge branch 'fix/fm_index_sentinels' into develop

* fix/fm_index_sentinels:
  [FIX] FMIndex: initialize first indicator positions in CSA construction
  [FIX] FMIndex: always initialize first sentinel positions to false during BWT construction
  [TEST] FMIndex: tested more specs