Addition CDI fixes. Made the ExecutionContext CDI only, which means that for non-CDI usage that thread local is not used (yay, microperformance).

But MOST importantly: the -Pcheck now runs green (at least on H2)!

Fixing up CDI multi instance test: making sequential MI is called consistently like parallel MI (ie. instances + 1)

Fix for SQL server failing with 'Prepared or callable statement has more than 2000 parameter markers' : added a configuration param that sets the max nr of insert statements in one bulk insert.

Manual merge of https://github.com/Activiti/Activiti/commit/a0c4a1881b5775b5156e9be9d29e099ac8a8afca to v6: still got to leave the optimize delete in here, as it optimizes the delete for execution (the order, which is quite important and cannot be deleted yet)

Manual merge of https://github.com/Activiti/Activiti/commit/60ae72ed924fc6426de0996e8ecdd2fd0a8de003 to v6

Manual merge of https://github.com/Activiti/Activiti/commit/e2f5d6ca5edb92ca0a27d6080b60c405ef07b745 to v6

Manual merge of https://github.com/Activiti/Activiti/commit/c4eb57ca7e1f101c0d7227c6cbba002155d84e81 to v6

Manual merge of https://github.com/Activiti/Activiti/commit/a8f730787b8d68805a805493b5bd07b212f77f13 to v6

Manual merge of https://github.com/Activiti/Activiti/commit/d7a966f0b65c1e0aa14fb75788f04ae569dbaa5a to v6: change to JobRetryCmd did not have to be applied on v6: process definition is not fetched, as the executionId is used to get the associated step in the process definition.

Manual merge of https://github.com/Activiti/Activiti/commit/d70b29b5426a1e579491e141a317fcb5ccb34ae4 to v6

Manual merge of https://github.com/Activiti/Activiti/commit/34fc5b80fabb9997579a14c2bca8b9eb33141d0a to v6

Manual merge of https://github.com/Activiti/Activiti/commit/db18e32bfb1f69699af82b9beb36ef5db9e652ff to v6

Manual merge of https://github.com/Activiti/Activiti/commit/4e4a190119813828af966c0e0bed6b193bc0ef04 to v6

Manual merge of https://github.com/Activiti/Activiti/commit/af5b2987bfc1d7dc279974e15f7eb54a1e940dc6 to v6

Manual merge of https://github.com/Activiti/Activiti/commit/806ac390a63a561759a5995ed24283391e6e8d4d to v6

Manually porting https://github.com/Activiti/Activiti/commit/f4dcc5ed3996e029ace1826bd6308c84668255eb to v6

Manual merge of https://github.com/Activiti/Activiti/commit/30bb3b60a634343bd7acfdcfd4c0517b4c23e13a to v6