[ticket/346] Use $config->set() instead of set_config()

B3P-346
[ticket/346] Correctly pass config object in calendar test

B3P-346
[ticket/346] Use phpBB log class instead of add_log()

B3P-346
[ticket/346] Use phpbb_get_avtar() instead of deprecated function

B3P-346
Merge pull request #348 from marc1706/ticket/346

[ticket/346] Remove usage of legacy phpBB functions and methods