Reformat everything

- Switch to a fairly standard code format. This is largely based on
   IntelliJ defaults, with some minor tweaks applied via editor config.
   Should mean people don't need to import a config!

 - Use "var" everywhere instead of explicit types. Type inference is a
   joy, and I intend to use it to its fullest.

 - Start using switch expressions: we couldn't use them before because
   IntelliJ does silly things with our previous brace style, but now we
   have the luxury of them!

buildSrc/src/main/kotlin/cc/tweaked/gradle/ProcessHelpers.kt

@@ -4,7 +4,6 @@ import org.codehaus.groovy.runtime.ProcessGroovyMethods
 import java.io.BufferedReader
 import java.io.IOException
 import java.io.InputStreamReader
-import java.util.stream.Collectors
 
 internal object ProcessHelpers {
     fun startProcess(vararg command: String): Process {
@@ -26,7 +25,7 @@ internal object ProcessHelpers {
 
     fun captureLines(process: Process): List<String> {
         val out = BufferedReader(InputStreamReader(process.inputStream)).use { reader ->
-            reader.lines().filter { it.isNotEmpty() }.collect(Collectors.toList())
+            reader.lines().filter { it.isNotEmpty() }.toList()
         }
         ProcessGroovyMethods.closeStreams(process)
         if (process.waitFor() != 0) throw IOException("Command exited with a non-0 status")