[FeatureRequest] filter for checking KSP version

[cake-pie]

KSP 1.4+ introduced some stock features (e.g. dynamic crew capacity, part variants) that, for part makers, offers a stock approach to accomplish some functions (e.g. texture switching, deployable/inflatable habitats) that would have previously required a bespoke plugin, or a dependency on another mod.

A :NEEDSKSP filter would provide the means to write one single config file that will adapt the part config according to what version of KSP the user has -- new stock features in 1.4+, or fall back on a legacy solution otherwise. This would be useful for not needing to maintain two different releases of a mod in order to support different KSP versions.

The filter should support value comparison >, <.
major.minor.patch for version numbers should be sufficient.
Would be nice if 1.4 were interpreted as 1.4.x as opposed to an explicit 1.4.0.

[blowfishpro]

This seems like a good idea. I would use :KSP_VERSION[x] though.

Agreed with respect to 1.4 matching any 1.4.* version.

I think we will need greater than or equal to and less than equal to. It should use whatever character we agree upon using for #99

[cake-pie]

:KSP_VERSION[x] looks good too.

Good points re: equality test, much more natural to specify gteq1.4.0 than having to contrive something along the lines of >1.3.9

[blowfishpro]

https://github.com/cake-pie/ModuleManager/tree/kspversion