modify checkpoint bugs

Signed-off-by: franklin <flin1866@gmail.com>
Merge remote-tracking branch 'remotes/spark/workspace'

Conflicts:
	src/main.cpp

modify checkpoint bugs
Signed-off-by: franklin <flin1866@gmail.com>
add CheckActiveChain at AppInit2()

Signed-off-by: franklin <flin1866@gmail.com>
modify nTargetSpacing

Signed-off-by: franklin <flin1866@gmail.com>
add a logically:only the SendCheckPoint is send and then send the lottkey.