Avoid missing events

[muhamadazmy]

The code improves chain events processing by making sure all blocks are processed. This is accomplished by

• Wait for new blocks
• Once a block is created, the block height is checked against the last processed block.
• All blocks from last processed block to current height is processed.
• Last processed block is stored in a temp file.
• On boot the system always uses the current block number as last processed block

Services that processes events still can be down when an event is received hence it doesn't also get a chance to handle the event. The recommended solution is that a service on start need to start listening to events then synchronize with the chain