SON11 - Add chain extension parameter to set SON count

[sierra19XX]

Add chain extension parameter to set SON count

LLD at https://peerplays.atlassian.net/wiki/spaces/PIX/pages/333971489/SON+Objects+and+Operators

[oxarbitrage]

Code looks good.

Unrelated to the code in this pull the base branch is failing in affiliate test case:

...
/home/oxarbitrage/CLionProjects/pp_pull135/peerplays/tests/tests/affiliate_tests.cpp(628): info: check 2 == idx.size() has passed
/home/oxarbitrage/CLionProjects/pp_pull135/peerplays/tests/tests/affiliate_tests.cpp(633): info: check 3 == idx.size() has passed
3392664ms th_a       affiliate_tests.cpp:730       test_method          ] 10 assert_exception: Assert Exception
result != std::shared_ptr<PluginType>(): 
    {}
    th_a  application.hpp:76 get_plugin
3392665ms th_a       db_management.cpp:187         close                ] Database close unexpected exception: {"code":10,"name":"assert_exception","message":"Assert Exception","stack":[{"context":{"level":"error","file":"fork_database.cpp","line":41,"method":"pop_block","hostname":"","thread_name":"th_a","timestamp":"2019-09-18T19:56:32"},"format":"_head: no blocks to pop","data":{}},{"context":{"level":"warn","file":"db_block.cpp","line":515,"method":"pop_block","hostname":"","thread_name":"th_a","timestamp":"2019-09-18T19:56:32"},"format":"","data":{}}]}
3392680ms th_a       db_management.cpp:187         close                ] Database close unexpected exception: {"code":3070001,"name":"pop_empty_chain","message":"there are no blocks to pop","stack":[{"context":{"level":"error","file":"db_block.cpp","line":507,"method":"pop_block","hostname":"","thread_name":"th_a","timestamp":"2019-09-18T19:56:32"},"format":"there are no blocks to pop","data":{}},{"context":{"level":"warn","file":"db_block.cpp","line":515,"method":"pop_block","hostname":"","thread_name":"th_a","timestamp":"2019-09-18T19:56:32"},"format":"","data":{}}]}
unknown location(0): fatal error: in "affiliate_tests/statistics_test": unknown type
/home/oxarbitrage/CLionProjects/pp_pull135/peerplays/tests/tests/affiliate_tests.cpp(633): last checkpoint
/home/oxarbitrage/CLionProjects/pp_pull135/peerplays/tests/tests/affiliate_tests.cpp(607): Leaving test case "statistics_test"; testing time: 3364770us
/home/oxarbitrage/CLionProjects/pp_pull135/peerplays/tests/tests/affiliate_tests.cpp(182): Leaving test suite "affiliate_tests"; testing time: 3364809us
Leaving test module "Master Test Suite"; testing time: 3364830us

*** 1 failure is detected in the test module "Master Test Suite"

This is not happening in the develop. Seems to be something related with the load of affiliate_stats_plugin.

Any input on what can be causing this ?

It will help if we can have gitlab CI passing on feature/SONs-base where we are pushing all the SON code.

[oxarbitrage]

We will fix the error in the test cases in another pr.

[bobinson]

LGTM