1.4.0

Bugfixes:

Issue #	Title
#2907	state_sync_routed_py_manytx_100 consistently fails after separating Peers into separate threads
#2906	clear_data can delete the same transaction twice, resulting in debug_assert

Improvements:

Issue #	Title
#2900	Investigate dropped messages
#2777	Add the fee for loading the contract into memory
#2751	Split VlewClient and Client into separate threads
#2732	DBCol should implement its own GC method
#1839	Error messages refactoring