adding option for hidding private exercises course -refs #7237
Create Clockworksms plugin; Implement in several mail sending calls - refs #7225
Merge branch '1.9.x' of https://github.com/chamilo/chamilo-lms into 1.9.x_clockworksms
Format code.
Adding default VisibilityAfterExpiration see BT#8606
Minor Cleaned code
Merge branch '1.9.x_clockworksms' of github.com:ilosada/chamilo-lms into ilosada-1.9.x_clockworksms
Remove useless files in clockworks plugin - refs #7225
Minor - format code.
Fixing session label see BT#8606
Merge branch '1.9.x' of ssh://github.com/chamilo/chamilo-lms into chamilo19
Minor - format code.
Adding export option in user information + forum and time info BT#7707
Minor - format code.
Fixing PHP notices see #7260
Fixing PHP notices see  #7260
Minor format code.
Adding work/forum stats data see BT#7707
Fixing lang var see BT#8646
Replacing mysql now() see BT#8397