fsm - rework just written FetchAndDownloadInventory

it can be written without recursive call to itself
previously written test passes (except few assertions which
test implementation details)
fsm - FetchAndDownloadInventory testing for JSON parsing

some code moved out to allow easy JSON parsing test,
JSON::XS boolean converted to real boolean
test parsing with real fixtures
FetchAndDownloadInventory JSON parsing - fix issue with versions 1.0 till 2.1
fsm - raise min version for JSON::XS (older are not compatible with testing
with boolean objects)