Fix: Alway display Available and Contracted field

Even if no time accounting is registred on a ticket we should display
the available and contracted field.
Mod: Base timeaccounting sum on current month.

If a ticket is handle on more than one month we have to compute time
accounting sum on the time accounting creation date instead of ticket
one.
Add: Ability to configure recurrence
Add: SupportQuota::Preferences::EmptyContractDisplay

This option allow you to specify if you want to alway display the
SuportQuota box.
SupportQuota: Review last pull request.

Some changes were necessary:

- IFNULL() SQL function is MySQL only. Remove it for compatibility.
  We have to find a way for better implement this;

- The proposed three SQL parts can fit in only two;

- Add a recurrence label to let the user know it;

- Apply OTRS code styling;

- Add the l10n strings for Brazilian Portuguese;

- Improvements and typos on module configuration text.
SupportQuota: merge revised pull request from @lermit.

- Fix display when no time accounting and add ability to configure
  recurrence.
SupportQuota: release 0.0.5.