Fixed toString method for Dictionary causing problems debugging when student iterator is not working
Fixed case "PART" should be case "QUIT" since the message that comes from the server is "QUIT" when someone quits the server.

A squash of:
AVLTree wording clarification
Update TopKSortTests.java
Bump up heap size in Gradle tests (thanks Marcus)
Fix various bugs with uMessage connection (thanks Zeynel)

All tests renamed and somewhat cleaned
corpus moved to separate folder
TopKSort clarification when k > array.length
AutocompleteTrie edits
Added part on AVLTree that they need correct internal structure