Add batch option

[StefanosChaliasos]

Compile multiple programs at once. This boosts up the throughput of the tool ~7 times.

After the merge of this PR, we can't use -r with -w, and -l has been removed. To run the tool with batch use --batch NUMBER_OF_ITERS_PER_BATCH.

TODOs:

• Handle KeyboardInterrupts.
• Add script to replay the transformations of a failed iteration.
• Update cronjobs to use --batch option

Closes #15

[StefanosChaliasos]

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