Create field formatting mechanism

[gabteles]

Fields not always should be displayed as they are in the database. Field formatters will receive an input from DB and process it to show as it should be in the interface.

Create:

• TotalFlex\Interfaces\IFieldFormatter
• TotalFlex\FieldFormatter\DateFromUnixtimestamp as a POC. It should receive an format (see strftime function formats) to instanciate it, a unix timestamp as input and should output a string in the corresponding format for the unix timestamp.

[hugoofab]

what do you think about strip out "I" prefix from interface names? Once it already is saved on "Interfaces" Folder