[-]BO: fix use of parameter class for renderForm()


In renderForm() and form.tpl, we can't use the parameter "class" for simple textarea instead of "textarea-autosize".
A "class" cannot be applied to a "textarea" if it has not the "class" autoload_rte.


To fix it, i propose: 
class="{if isset($input.autoload_rte) && $input.autoload_rte}rte autoload_rte {if isset($input.class)}{$input.class}{/if}{else}{if isset($input.class)}{$input.class}{else}textarea-autosize{/if}{/if}"

Best regards
// fix small bug with optin during install
// productcomments : removed capitalize on title
// wording
//[*] BO : fix module toolbar icon
Merge branch '1.6' of https://github.com/PrestaShop/PrestaShop into 1.6
Merge pull request #1440 from djfm/install

// fix small bug with optin during install
[*] FO : inline review stars
// missing index in meta
Merge branch '1.6' of https://github.com/PrestaShop/PrestaShop into 1.6
[*] FO : inline/align review stars
// dashproducts : norm
// dashgoals : norm
//dashactivity : norm
// add a button to enable real time on the dashboard
Merge branch '1.6' of https://github.com/PrestaShop/PrestaShop into 1.6
Merge branch '1.6' of https://github.com/PrestaShop/PrestaShop into 1.6
// bxslider blockcart
// push on dashproducts
// Fixed one case of current tab highlighting