all: Audit gitignore Contents

Problem / Solution

Our open source project gitignore files have accumulated quite a bit of
cruft. Let's unify them, remove no longer necessary entries, and call
out project specific items.

JIRA Issues: CSL-7911

Differential Revision: https://phabricator.twitter.biz/D311962

.gitignore

@@ -1,21 +1,19 @@
-target/
-scrooge-benchmark/src/generated
-scrooge-core/target/
-scrooge-runtime/target/
+*.class
+*.iml
+*.ipr
+*.log
+.DS_Store
+.cache
+.history
+.idea/
+.lib
 dist/
+lib_managed/
+out/
 project/boot/
 project/plugins/project/
-project/plugins/src_managed/
-*.log
-*.tmproj
-lib_managed/
-*.iml
-.idea/
-.classpath
-.project
-.scala_dependencies
-.ivyjars
-.classpath.txt
 sbt-launch.jar
-.gcprof
-allocation.jar
+target/
+
+# Scrooge specific
+.classpath.txt