Bug 1940611 - Update README.Mahara on removed files

- RecordSet_postgres7->MoveNext() - remove expensive is_array() (04ef8a3b9770f93326a2ece31e4089368117faca)

- Allow check for $okversion of Postgres or MySql: Minimum working version values should be in updated in Mahara's README.md file and in init.php

- Check for valid columns in adodb postgres64 driver MetaIndexes fn (b87d9961020a8d52a2eaf709a9197520b3c6b65b)

- Deleted many files/folders we're not using: /cute_icons, /tests, /docs, /drivers except non-deprecated mysql and postgres, /datadict except mysql and postgres, /lang except english, /pear, /perf, /replicate, .git*, mailmap.

- Modified session variable setting from $_SESSION to $SESSION->set/get due to sessions now normally being closed. (f9818ff606bbe6ec00b34eab23d1743870407b48)

- Bug 1619036: Fix a bug when determine if an array is associative (606317195f8f3a8cdf9bc448c537b8c3708d75d7)

- Removing the obsolete adodb-mysql.inc.php (2f19a42ddd6af732e40b1aae9359ee80e28f9111)

- escaping names when showing table / index in adodb-mysqli.inc.php(08939ca25acddff39b132e4bd823668b98447947)

- The lastest version comes with a Load balancer class and a tuning class which we don't use yet so they are not put in.

- Deleted many files/folders we're not using:

  - Removed files

    - adodb-loadbalancer.inc.php

    - adodb-perf.inc.php

    - composer.json

  - Removed directories

    - /datadict except mysql and postgres

    - /docs

    - /pear

    - /perf

    - /phpdoc

    - /session

    - /lang except EN

    - /drivers except: (non-deprecated mysql and postgres) adodb-mysqli.inc.php, adodb-postgres64.inc.php, adodb-postgres7.inc.php