I do know Multiple dex problems have been reported a lot of times before, but i none of the solutions seem to work in my case.
Unable to execute dex: Multiple dex files define Lbolts/AggregateException;
Conversion to Dalvik format failed: Unable to execute dex: Multiple dex files define Lbolts/AggregateException;
what was actually causing the trouble is the bolts-android library. there were two DIFFERENT versions of it conflicting. the facebooksdk comes with bolts-android-1.1.2 and appcompatv7 comes with 1.1.4.
I unmarked Android Private Libraries container in the FacebookSDK library project, which contained bolts-android-1.1.2. As a result, my project now had only one version, 1.1.4
it runs fine now
turns out, the duplicate appcompatv7 entries were never troubling