Gitignore cleanup

Since `.idea/` is in the list, all other patterns that start with `.idea/` are redundant.

Also: ignore MacOS metadata files named `.DS_Store`

.gitignore

@@ -1,47 +1,10 @@
 # Created by https://www.gitignore.io/api/sbt,scala,intellij+all
 # Edit at https://www.gitignore.io/?templates=sbt,scala,intellij+all
-
-### Intellij+all ###
-# Covers JetBrains IDEs: IntelliJ, RubyMine, PhpStorm, AppCode, PyCharm, CLion, Android Studio and WebStorm
-# Reference: https://intellij-support.jetbrains.com/hc/en-us/articles/206544839
-
-# User-specific stuff
-.idea/**/workspace.xml
-.idea/**/tasks.xml
-.idea/**/usage.statistics.xml
-.idea/**/dictionaries
-.idea/**/shelf
-
-# Generated files
-.idea/**/contentModel.xml
-
-# Sensitive or high-churn files
-.idea/**/dataSources/
-.idea/**/dataSources.ids
-.idea/**/dataSources.local.xml
-.idea/**/sqlDataSources.xml
-.idea/**/dynamic.xml
-.idea/**/uiDesigner.xml
-.idea/**/dbnavigator.xml
-
-# Gradle
-.idea/**/gradle.xml
-.idea/**/libraries
-
-# Gradle and Maven with auto-import
-# When using Gradle or Maven with auto-import, you should exclude module files,
-# since they will be recreated, and may cause churn.  Uncomment if using
-# auto-import.
-# .idea/modules.xml
-# .idea/*.iml
-# .idea/modules
+# Manually edited since.
 
 # CMake
 cmake-build-*/
 
-# Mongo Explorer plugin
-.idea/**/mongoSettings.xml
-
 # File-based project format
 *.iws
 
@@ -54,21 +17,12 @@ out/
 # JIRA plugin
 atlassian-ide-plugin.xml
 
-# Cursive Clojure plugin
-.idea/replstate.xml
-
 # Crashlytics plugin (for Android Studio and IntelliJ)
 com_crashlytics_export_strings.xml
 crashlytics.properties
 crashlytics-build.properties
 fabric.properties
 
-# Editor-based Rest Client
-.idea/httpRequests
-
-# Android studio 3.1+ serialized cache file
-.idea/caches/build_file_checksums.ser
-
 # JetBrains templates
 **___jb_tmp___
 
@@ -113,4 +67,7 @@ project/plugins/project/
 
 # End of https://www.gitignore.io/api/sbt,scala,intellij+all
 
-.vscode
+.vscode
+
+# MacOS
+.DS_Store