Validate Table Resumption Functionality

[jtesta]

Table generation can (in theory) be interrupted and resumed. The code was functioning in early alpha releases, but has not since been tested. A warning is issued to the user upon resumption that it is still experimental and may result in wasted effort (as the resulting table may end up corrupt).

Testing should be done on the resumption functionality to ensure that it is of production quality. If possible, a test should be made in crackalack_tests.py. Lastly, the warning should be removed.