Implement postLS1 as an Era - core parts

[mark-grimes]

This is the first part of a split down #6784. The only thing it adds is

• an "--era" option to cmsDriver
• 3 blank eras (i.e. they don't do anything yet) - run2, bunchspacing25ns and bunchspacing50ns
• a new customise function customiseRun2EraExtras which currently is a direct copy of customisePostLS1

bunchspacing25ns and bunchspacing50ns are not intended to be specified by the user, ConfigBuilder adds them automatically depending on what pileup is requested.
run2 will eventually be the customisePostLS1 customisation implemented as an era. Each portion will be added incrementally in further pull requests. Until it is complete, the customiseRun2EraExtras customisation can be used to do the parts that haven't been implemented yet (currently everything).
So commands that originally had

--customise SLHCUpgradeSimulations/Configuration/postLS1Customs.customisePostLS1

can be tested using eras with:

--era run2 --customise SLHCUpgradeSimulations/Configuration/postLS1Customs.customiseRun2EraExtras

Eventually when run2 is fully implemented the customisation will not be required.

I tested the 1320.0 workflow (since it is one of the postLS1 ones) with and without the above replacement, then diff-ed the resulting configuration files and diff-ed the result of applying edmConfigDump on those files. There is absolutely no difference in the dumps, for the files themselves there are small expected differences (different customisation name, run2 era specified). Note that diff equivalency is not expected once run2 actually does something, for reasons that will be explained in the relevant subsequent pull requests.

@davidlange6, @Dr15Jones

@franzoni - this is just the core parts, it doesn't show how to use the eras yet. I'll ping you again when there is a good example (or you can look at #6784 but there's a lot in there to wade through).

[cmsbuild]

A new Pull Request was created by @mark-grimes (Mark Grimes) for CMSSW_7_4_X.

Implement postLS1 as an Era - core parts

It involves the following packages:

Configuration/Applications
Configuration/StandardSequences
SLHCUpgradeSimulations/Configuration

@civanch, @nclopezo, @mdhildreth, @cmsbuild, @franzoni, @davidlange6 can you please review it and eventually sign? Thanks.
@ghellwig, @Martin-Grunewald, @makortel, @GiacomoSguazzoni, @rovere, @VinInn, @appeltel, @cerati, @dgulhan this is something you requested to watch as well.
You can sign-off by replying to this message having '+1' in the first line of your reply.
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[ghost]

@cmsbuild please test

[cmsbuild]

The tests are being triggered in jenkins.

[cmsbuild]

+1
Tested at: 11403f2
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-7419/2196/summary.html

[civanch]

+1

[davidlange6]

+1

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_4_X IBs unless changes (tests are also fine). This pull request will be automatically merged.