Refactor OT extension to allow semi-honest

[jot2re]

Currently our OT extension implements the KOS15 protocol to achieve malicious security. However, by simply skipping the correlation check in RotReceiverImpl/RotSenderImpl yields a semi-honest OT extension similar to that of IKNNP03 ("Extending Oblivious Transfers Efficiently"). The task is to refactor this implementation in a sensible manner so that we will get access to both a malicious and semi-honest OT extension. Finally with this semi-honest OT in place, change the TinyTables implementation to have it use the semi-honest implementation rather than the malicious one.