[ticket/12890] Add basic function to CPF framework for searching

These will later be used to allow searching with respect to each custom
profile filed

PHPBB3-12890
[ticket/12890] Implement basic search backend for member list

Still not completed yet, needs more work especially tempting and field
specific search conditions in a few cases such as the date field.

PHPBB3-12890
[ticket/12890] Fix minor errors

PHPBB3-12890
[ticket/12890] Allow specifying table alias for search SQL

PHPBB3-127890
[ticket/12890] Add custom profile field search fields in template

Currenty needs to be divided into two columns

PHPBB3-12890
[ticket/12890] Load CPF before sorting data is arranged

PHPBB3-12890
[ticket/12890] Join users and cpf data table while searching

PHPBB3-12890
[ticket/12890] Implement CPF sorting on memberlist

PHPBB3-12890