Update to allow Alignment to run multithreaded

Modifications to allow running multithreaded:

• rewrote AlElementHistos to use Accumulator::Histogram
• changed from mutex to shared_mutex to profit from readonly locks
• create AlEquations object in each event call on the stack and add at end of event to minimize number of write locks
• AlignAlgorithm no longer derives from GaudiHistoAlg
• update gaudiiter to support running multi-threaded (works on MDF files only)

This addresses most of what is discussed in #30

This also fixes a crash in a test on clang that was due to a bug in the IO of the Al::Equations object.

@graven, @jcobbled

marked this merge request as draft

mentioned in issue #30

added RTA label

added 21 commits

• c8a5f354...eb51d61f - 17 commits from branch master
• cf12accd - - make 'add' method more suitable for frequent use
• d98d354d - updated settings for running gaudiiter multithreaded
• ec67ca0b - update to allow running in multithreaded mode:
• 796b50d8 - fixed typo in last commit

Compare with previous version

added 1 commit

• f9d33d1f - Fixed formatting

Compare with previous version

resolved all threads

added 1 commit

• f3393c6e - replace boost::lexical_ cast by to_string

Compare with previous version

added 1 commit

• 987cef3a - don't template AlElementHistos as it is not necessary

Compare with previous version

added 1 commit

• 6c2be446 - Fixed formatting

Compare with previous version

added 3 commits

• b0878a30 - - bug fix for clang (template<> missing)
• 0bec3f4a - write output file from AlignAlgorithmBase::stop in offline environment
• 73fc7aeb - use gaudirun.py rather than gaudiiter.py in analyzer test

Compare with previous version

changed title from Draft: Next update to allow Alignment to run multithreaded to Draft: Update to allow Alignment to run multithreaded

changed the description

added 1 commit

• 30111ad0 - Fixed formatting

Compare with previous version