Fix optional resources.

Correctly set the optional flag in the ResourceRate constructor and
preserve it when building the output rates array.
Correct some whitespace issues.
Add the OutputRates to the final list.

I had failed to notice the difference between OutputRatios and OutputRates
(I was wondering why things were done twice...)
Cache loaded rates
Rebalance converters
Add cost to Kethane
Removed logarithmic timewarp factor
Update compatible version to KSP 0.24
Adjusted part costs for career mode
Version 0.8.7
Upgrade CompatibilityChecker to version 3
Update compatible Unity version to 4.5.2
Fix compatible Unity version (it ends with 'f1')
Version 0.8.8
Call GetConnectedResources with the resource's flow mode.

0.24.1 added the extra parameter, presumably as a fix for the vernor issue
(I haven't looked that deeply). It seems that it is possible to override a
resource's flow mode, but I chose to keep Kethane's behavior with respect
to LiquidFuel and Oxidizer the same as in earlier versions.
Update CC for KSP 0.24.2
Set version to 0.8.8.1

This is just to distinguish this fixed Kethane from Majiir's official
versions.
Move Cell to its own namespace
Lift Cell.Map to a namespace-level class
Lift Cell.Set to a namespace-level class