[acm.c,acme.c] Add keepalive configuration parameter to ACM.
Add reconect

ssa.c: Remove trailing whitespace

ssa.c: Skip reconnect if max. count is reached

ssa.c: Add  ssa_upstream_stop_reconnection_timer function

ssa.c: Fix some issues in reconnect

ssa.c: Add global variables for max. reconnect attempts and timeout.

ssa.c: Zero reconnect counter after new join.

ssa.c: Add new reconnection case

ssa.c: Add cases for reconnect_max_count and reconnect_timeout = 0

ssa.c: Change default values for reconnect_timeout and
reconnect_max_count
acm,distrib: Add reconnect_max_count and reconnect_timeout configuration
parameters.

 reconnect_max_count specifies max. number of reconnection to the
 upstream node. If the number is reached the node rejoins to
 distribution tree and asks for a new parent.
 reconnect_max_count < 0, reconnection is disabled.
 reconnect_max_count = 0, rejoin without reconnection.
 Default value is 10.

 reconnect_timeout specifies timeout (in sec.) between reconnections.
 reconnect_timeout < 0, reconnection is disabled.
 Default value is 10.
ssa.c: Fix case with reconnect_timeout == 0
ssa.c: Fix if that checks if reconnection is disabled
ssa.c: Fix some issues in reconnect
ssa.c: Add random shift in reconnection process.

 The random shift helps to avoid massive nodes reconnection at
 the same time.