Allow search multiple values in dashboard widgets

Example of widget needing this patch :

```
<?xml version="1.0" encoding="utf-8"?>
<otrs_config version="1.0" init="Application">

<ConfigItem Name="DashboardBackend###0910-TicketOpen-Unlocked" Required="0" Valid="1">
  <Description Lang="en">Parameters for the dashboard backend. ...</Description>
  <Group>Ticket</Group>
  <SubGroup>Frontend::Agent::Dashboard</SubGroup>
  <Setting>
   <Hash>
    <Item Key="Module">Kernel::Output::HTML::DashboardTicketGeneric</Item>
    <Item Key="Title">Tickets à traiter</Item>
    <Item Key="Description">Tickets ouverts et déverrouillés</Item>
    <Item Key="Attributes">StateIDs=1,4,6;LockIDs=1;</Item>
    <Item Key="Filter">All</Item>
    <Item Key="Time">Age</Item>
    <Item Key="Limit">30</Item>
    <Item Key="Permission">rw</Item>
    <Item Key="Block">ContentLarge</Item>
    <Item Key="Default">1</Item>
    <Item Key="CacheTTLLocal">0.5</Item>
    <Item Key="DefaultColumns">
     <Hash>
      <Item Key="Age">2</Item>
      <Item Key="TicketNumber">2</Item>
      <Item Key="Title">2</Item>
      <Item Key="Owner">2</Item>
      <Item Key="Queue">2</Item>
      <Item Key="Changed">1</Item>
      <Item Key="CustomerID">1</Item>
      <Item Key="CustomerName">1</Item>
      <Item Key="EscalationResponseTime">1</Item>
      <Item Key="EscalationSolutionTime">1</Item>
      <Item Key="EscalationTime">1</Item>
      <Item Key="EscalationUpdateTime">1</Item>
      <Item Key="Lock">1</Item>
      <Item Key="PendingTime">1</Item>
      <Item Key="Priority">1</Item>
      <Item Key="Queue">1</Item>
      <Item Key="Responsible">1</Item>
      <Item Key="SLA">1</Item>
      <Item Key="Service">1</Item>
      <Item Key="State">1</Item>
      <Item Key="Type">1</Item>
     </Hash>
    </Item>
   </Hash>
  </Setting>
 </ConfigItem>
</otrs_config>
```