EXCERPT: Since 1992, the Immigrant Learning Center has taught English and other skills to about 3,000 adult immigrants in three dozen Eastern Massachusetts communities.  Now it also wants to educate the public at large – about immigrants. Diane Portnoy, cofounder and director of the Malden-based center, said she hopes to initiate a human rights institute at the center next year that would raise awareness about what she says are the positive contributions that immigrants make to society.