Deprecate Version 1 configuration

[nathanjrobertson]

As per messages on slack, now that a full release (1.4.0) has been released, we'll now mark the old Version 1 configuration as deprecated. In this PR:

• Documentation updated to announce the deprecation and encourage migration to V2 configuration.
• The contents of the old SQL.php and PasswordVerify.php files are replaced to simply redirect to the new SQL1Compat.php and PasswordVerify1Compat.php compatibility interfaces. Eventually we'll remove these as well.
• Logging messages in SQL1Compat.php and PasswordVerify1Compat.php are added to warn people they are using deprecated interfaces.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 56.76%. Comparing base (bb5486a) to head (2f86bb8).
⚠️ Report is 5 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master      #27      +/-   ##
============================================
- Coverage     59.60%   56.76%   -2.85%     
+ Complexity      148      104      -44     
============================================
  Files             5        3       -2     
  Lines           666      525     -141     
============================================
- Hits            397      298      -99     
+ Misses          269      227      -42     

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.