Rename Bell run/ to run_jobs/ and merge Hadoop examples

Rename the Bell "run" directory to "run_jobs" and move run.md to
run_jobs/index.md for consistency with other user guides. Update all
internal links, nav, breadcrumbs, and the shared Fluent snippet
accordingly. Merge the HBase, Hive, and Pig examples into a single
hadoop.md and remove the now-orphaned per-topic snippets. Also fix a
"Running Jobs" heading typo in the Gautschi guide.

Author: Guangzhen-Jin

docs/assets/data/breadcrumbs.json

@@ -140,7 +140,7 @@
     "Bell User Guide",
     "Software"
   ],
-  "/userguides/bell/run/": [
+  "/userguides/bell/run_jobs/": [
     "Home",
     "Bell User Guide",
     "Running Jobs"