[ticket/13126] Improve the feedback when running the migrations

PHPBB3-13126
[ticket/13126] Extends migrator_output_handler instead of using a closure

PHPBB3-13126
[ticket/13126] Move migrator_output_handler to an interface

PHPBB3-13126
[ticket/13126] Change messages verbosity levels

PHPBB3-13126
[ticket/13126] Fix tests

PHPBB3-13126
[ticket/13126] Add missing use statement

PHPBB3-13126
[ticket/13203] Add method for byte by byte comparison to drivers helper

PHPBB3-13203
[ticket/13203] Use string_compare method in passwords drivers

PHPBB3-13203
[ticket/13203] Fix passwords manager tests

PHPBB3-13203
Merge pull request #3056 from marc1706/ticket/13203

[ticket/13203] Use constant time comparison method for comparing password hashes
[ticket/security-159] Only show first 8 characters of login keys in UCP

SECURITY-159
[ticket/13205] Add a mark all messages read link to PM folders

PHPBB3-13205
Merge pull request #3057 from marc1706/ticket/security-159

[ticket/security-159] Only show first 8 characters of login keys in UCP
[ticket/13205] Remove superfluous newline

PHPBB3-13205
[ticket/13205] Explicitly cast ids to integers and reformat SQL

PHPBB3-13205
Merge pull request #3058 from naderman/ticket/13205

[ticket/13205] Add a mark all messages read link to PM folders
[ticket/security-161] Add form token to styles management form.

SECURITY-161
Merge pull request #3 from phpbb/ticket/security-161

[ticket/security-161] Add form token to styles management form.
[prep-release-3.1.0-RC6] Update version to 3.1.0-RC6
[prep-release-3.1.0-RC6] Add migration for 3.1.0-RC6