Fix EZP-21977: improve output of binary field filesize

<h2> Link </h2>
See http://jira.ez.no/browse/EZP-21977
<h2>Description</h2>
The goal of the story here is that ez_render_field() when called on a binary file display the size in bytes and that it automaticaly choose the right unit. To do that I created a twig filter named ez_file_size which will display the unit size ( e.g. B, KB, MB, GB ...). 
There is also internationalization here to display the right pattern, this is mostly only used to vary between point and coma pattern ( e.g. 3,4 MB / 3.4 MB ).
The twig filter can be called like that : {{ 656556|ez_file_size( 3 ) }} where the first number will be converted with the correct unit size, and the parameter is the number of decimal we will get ( here we will have, with a french site access, 656,556 kB in outpout for example ).

<h2> Tests </h2>
 unit tests with twig data provider