Split integrations and export into ext module

feat: move integrations from lib to ext
feat: move content export from lib to ext
feat: rename affected packages for separate module distribution
chore: update Gradle module wiring
chore: adjust JPMS descriptors and dependencies
docs: update module structure documentation

ext/.project

@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<projectDescription>
+	<name>ext</name>
+	<comment>Project ext created by Buildship.</comment>
+	<projects>
+	</projects>
+	<buildSpec>
+		<buildCommand>
+			<name>org.eclipse.jdt.core.javabuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+		<buildCommand>
+			<name>org.eclipse.buildship.core.gradleprojectbuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+	</buildSpec>
+	<natures>
+		<nature>org.eclipse.jdt.core.javanature</nature>
+		<nature>org.eclipse.buildship.core.gradleprojectnature</nature>
+	</natures>
+</projectDescription>