When upgrading or downgrading the inventory_sync plugin it's possible
an different structure of the global.inventory_sync table is left behind
which could cause the code to crash when certain sub tables are not
present.
Be more defensive in the initialization of the table to make sure all
sub-tables are present on startup.
* New method avoids all dataloss and prefectly replicates the queue
* Made proper description in readme
* Added packages to make lerna build happy
* Added reference to main readme