[ticket/12132] Add viewtopic_print_head_append event to subsilver2

PHPBB3-12132
[ticket/12132] Add the event to events.md doc

PHPBB3-12132
[ticket/12134] Add ucp_pm_viewmessage_print_head_append event to subsilver2

PHPBB3-12134
[ticket/12115] Convert user occupation to a profile field

PHPBB3-12115
[ticket/12115] Add language entries for the profile fields

PHPBB3-12115
[ticket/12115] Remove occupation field from html files

PHPBB3-12115
[ticket/12115] Translate profile field name before displaying it in errors

PHPBB3-12115
[ticket/12115] Add methods to interface

PHPBB3-12115
[ticket/12115] Remove old language strings

PHPBB3-12115
[ticket/12115] Also port user interests to profile fields

PHPBB3-12115
[ticket/12115] Add a new migration for profilefield_interests

With this we avoid missing to copy one, when the admin already created
a phpbb_* profile field.

PHPBB3-12115
[ticket/12115] Use base class to reduce duplicate code

PHPBB3-12115
[ticket/12115] Add migration file to remove old user columns

PHPBB3-12115
[ticket/12115] Remove space from line ending

PHPBB3-12115
[ticket/12170] Assign schema keys in migration helper with data_depth 1

The migration helper currently drops any keys with schema changes that have
the data_depth 1. This change will correctly assign the keys to the steps
array without dropping the keys that might contain important info like the
actual table that should be created.

PHPBB3-12170
[ticket/12170] Test for 12170

PHPBB3-12170
Merge remote-tracking branch 'exreaction/ticket/12170' into ticket/12170
[ticket/12141] Disable opcache on travis for php 5.5.8 aswell

PHPBB3-12141
Merge pull request #2017 from nickvergessen/ticket/12141

[ticket/12141] Disable opcache on travis for php 5.5.8 aswell

* nickvergessen/ticket/12141:
  [ticket/12141] Disable opcache on travis for php 5.5.8 aswell
[ticket/12175] Fix upload test for empty file

PHPBB3-12175