Updates for trigger + install grid submit scripts

This is mainly fixes for issues that @viruelas and I found while trying to submit jobs to make trigger training datasets.

I also took the opportunity to clean up a bit more generally by installing the grid submission scripts as part of the build job. This means once the package is built and you source the setup.sh script, you should be able to run it from anywhere without writing the full path to the grid submission scripts.

Specific changes:

• submit-single-btag, submit-hbb, and submit-trigger were added to the installed scripts. I dropped the .sh suffix and renamed submit.sh to submit-single-btag to be a bit more explicit. They all required a bit of internal tweaking to make sure they could find the source directory.
• Deleted grid/build.sh and grid/run.sh which don't do anything anymore (they were useful back when we'd build on grid sites).
• Clean up submit-trigger a bit: now to submit a batch of jobs I use xargs to keep a constant queue of 10 (or some other configurable number) submitting at once. Before the script would submit one every second and then wait for them all to finish.
• Update submit-trigger to submit over the samples in ATLMCPROD-9424. Update the trigger we use to HLT_j20_0eta290_020jvt_pf_ftf_boffperf_L1J15
• Update README.md to explain any changes.