preview for SPK support

Preview for implementation of support for SPK kernels.

This includes readers and evaluators for all types of SPK.

I'm still in the process of adding proper documentation, additional checks, Orekit exceptions and a few other checks, but thought it would be a good idea to provide this draft/preview in case the team wants to have a look already!

src/test/java/org/orekit/files/daf/DAFParserTest.java

@@ -61,7 +61,7 @@ public class DAFParserTest {
         Assertions.assertEquals(6, testFileRecord.getNumIntsSummary());
         Assertions.assertEquals(5, testFileRecord.getSingleSummarySizeDoubles());
         // comments tests
-        Assertions.assertEquals(296, testComments.length());
+        Assertions.assertEquals(297, testComments.length());
         // array tests
         Assertions.assertEquals("vgr2.jup230.nio", testArray.getArrayName());
         Assertions.assertEquals(4097, testArraySummary.getInitialArrayAddress());