Adding table width percentagens to design-forum

Forum layout was massy at forums if chosen design-theme (http://cirandas.net/myprofile/ees-teste-formiga/themes) were default (blocks on the left and right sides and block at center).

Error were at https://cirandas.net/cirandeiros/materiais-para-formacao/materiais-didaticos/forum-de-discussao-sobre-materiais-didaticos?view=true, when it were theme default