[RTA DPA BW Tests] Documentation

Written including the following changes:

• HLT2 BW Test on Data : !3644 (merged)
• improved configurability: lhcb-datapkg/PRConfig!449 (merged)
• Clarity in comparison pages and instructions: lhcb-core/LHCbPR2HD!299 (merged)

Update HLT1 BW Sequence

!3837 (1396dd27).
Noticed Hlt1 BW sequence needed updating.
Trivial change, but expect a significant change in the BW Test

ToDo:

• Reread before review : results placed in /eos/lhcb/user/l/lugrazet/public/BWTesters/Documentation
• Review from @rjhunter
• CI-test with lhcb-datapkg/PRConfig!449 (merged), again, now we are on master
• Wait for lhcb-datapkg/PRConfig!413 (merged) to be merged, then rebase
• Merge with lhcb-datapkg/PRConfig!449 (merged) + lhcb-core/LHCbPR2HD!299 (merged)