Fixes #2157: The '*' category pattern will match all categories that do not match any other patterns listed in `I18N::translations`

fixes #2132, fixes #2133

- DbMessageSource now performs UNION ALL.
- Fixed message merging for php and po.
- Updated tests.

Added one line about support of UNION ALL queries.

Change <code>array_reduce</code> with anonimous function variant to easy string collection from pieces of unions.

Using short array syntax.

Change buildUnion method to be ready to accept parameters in <code>['all' => $all, 'query' => $query]</code> format for division to "UNION" and "UNION ALL" constructions.

Change passing parameters to array with two elements – 'all' which means if we use UNION or UNION ALL construction and 'query' which is our sql query that will be at right of construction.

in case no dir is present

Forget one ";" :D

Delete some spaces from result string.

Change union method to accept also <code>$all</code> variable. TRUE means that we must results <code>UNION ALL</code> construction, FALSE – that <code>UNION</code>.