Improve database column references and default category handling (#563)

* Improve default category handling and add cascade to references where possible

* Minor fix for default category

* Make the default category always first in the normalization

server/src/test/kotlin/suwayomi/tachidesk/manga/controller/UpdateControllerTest.kt

@@ -71,7 +71,6 @@ internal class UpdateControllerTest : ApplicationTest() {
                 it[title] = _title
                 it[url] = _title
                 it[sourceReference] = 1
-                it[defaultCategory] = true
                 it[inLibrary] = true
             }.value
         }

server/src/test/kotlin/suwayomi/tachidesk/test/TestUtils.kt

@@ -38,7 +38,6 @@ fun createLibraryManga(
             it[title] = _title
             it[url] = _title
             it[sourceReference] = 1
-            it[defaultCategory] = true
             it[inLibrary] = true
         }.value
     }