Enclave memory improvement

[cankisagun]

Increase enclave memory limit from 4kB to 128MB or 4GB.

The amount of data that the enclave is capable of storing encrypted (through a process known as sealing and unsealing is currently limited to 4kB. This is obviously not limited by disk space, but by the fact that the amount of data to seal/unseal needs to fit inside the enclave memory. Intel SGX documentation states that the enclave limit is 4GB, which should be tested for this particular application. The current limit is controlled by SEAL_LOG_SIZE in [enclave/src/data.rs] around Line 25. This value needs to at most equal to HeapMaxSize defined in [enclave/Enclave.config.xml]