BMRB refactor

[rvhonorato]

This PR refactors the way the BMRB table is used in FANDAS.

Since there was no input format before, the user would input a simple text file and then manually tell the code which column contained which information via sequence_start, resnum_column and chemical_shift_column.

However, BMRB has the very nice NMR-STAR format that should be used instead, its highly documented and BMRB itself provides a conversion tool from other formats to it.

With this enhancement we can drop the column parameters and substitute it for a target_entity that will tell FANDAS which entity from the BMRB file it should use.

The NMR-STAR format also contains sequence information, which can then in turn be used to match the input sequence with the BMRB entity, thus allowing for a great flexibility when using BMRB files.

# ...
 [2022-08-01 17:48:47,545 main:L99 INFO] Assigning chemical shifts
 [2022-08-01 17:48:47,545 assign:L34 INFO] Loading standard chemical shifts from /Users/rodrigo/repos/fandas/src/fandas/data/standard.csv
 [2022-08-01 17:48:57,012 use_bmrb:L68 INFO] Aligning input sequence with BMRB entity 1
 [2022-08-01 17:48:57,038 align_to:L52 INFO] Identity: 100.00%
 [2022-08-01 17:48:57,039 align_to:L54 INFO] ------TLTGKTITLEVEPSDTIENVKAKIQDKEG-----QRLIFAGKQLEDGRTLSDYNIQKESTLHLVLRLRGG
 [2022-08-01 17:48:57,039 align_to:L54 INFO] ------|||||||||||||||||||||||||||||-----||||||||||||||||||||||||||||||||||||
 [2022-08-01 17:48:57,039 align_to:L54 INFO] MQIFVKTLTGKTITLEVEPSDTIENVKAKIQDKEGIPPDQQRLIFAGKQLEDGRTLSDYNIQKESTLHLVLRLRGG
 [2022-08-01 17:48:57,039 use_bmrb:L70 INFO] Updating shifts based on BMRB table
 [2022-08-01 17:48:57,039 _update_shifts:L85 INFO] # (bmrb.7) 7 T       H       8.22    >> 8.72
# ...