Prepare release of Bolt 3.6.7 (bolt#7771)

* Make sure `accept_file_types` is an INDEXED array

* Blacklist some common PHP file extensions

* code formatting

* Refactored the thing

* CS fixes

* Fix typo.

* Third time's a charm

* Remove outdated comment

* Add a description in config

* Prepare release of Bolt 3.6.7

* Update config.yml.dist

* Compare filename extension lowercased

* Prepare release of Bolt 3.6.7

* Updating changelog / lock

Merge pull request bolt#7757 from bolt/release/3.6.6

Preparing release 3.6.6

Merge pull request bolt#7746 from bolt/release/3.6.5

Prepare for release of Bolt 3.6.5

Merge pull request bolt#7734 from bolt/release/3.6.4

Preparing release 3.6.4.

Merge pull request bolt#7724 from bolt/release/3.6.3

Preparing release Bolt 3.6.3

Merge pull request bolt#7713 from bolt/release/3.6.2

Prepare release of Bolt 3.6.2

Merge pull request bolt#7706 from bolt/release/3.6.1

Preparing release 3.6.1

Merge pull request bolt#7687 from bolt/release/3.6.0

Prepare release 3.6.0

Merge branch '3.6' of github.com:bolt/bolt into 3.6

Merge pull request bolt#7673 from bolt/release/3.6.0-beta6

Prepare release Bolt 3.6.0 beta 6