NaNChecker: self-generate NaNs or test

[Roland Haas]

https://bitbucket.org/cactuscode/cactusutils/pull-requests/10/rhaas-make-nans/diff

implements a short helper routine to fill a grid function with NaNs for tests.

It also changes the schedule so that schedule.ccl does no longer depend on STEERABLE=always parameters (either that or making the parameters STEERABLE=recover is required to ensure correct behaviour).

Minor since it does not affect actual simulations (only the test) for the most part, should go into the release though.

Keyword: NaNChecker

[Roland Haas]

Applied in git hash 05b9f1b of CactusNumerical.