Merge pull request #62 from chamilo/1.9.x

1.9.x
remove 'overwrite' comment
Allow ExtraFieldValue::get_item_id_from_field_variable_and_field_value() to return the last value instead of the first - refs BT#8392
Solve bug con course block - refs BT#7210
Merge pull request #320 from AngelFQC/7210

Solve bug con course block - refs BT#7210
Fix deadlock condition in documents download
Merge branch '1.9.x' of github.com:chamilo/chamilo-lms into 1.9.x
Update INSTALL
merge
Fix download page link
A day has 86400 seconds, not 84600.
Solves Bug#7179

Solves problem editing password when username=email
Fixing hide buttons see BT#8417
Minor update docs + format code
Merge branch '1.9.x' of ssh://github.com/chamilo/chamilo-lms into chamilo19
Update changelog in prevision of 1.9.8.3
Merge branch '1.9.x' of github.com:chamilo/chamilo-lms into 1.9.x
check token to avoid CSRF - refs BT#7215
Fixing PHP warnings see BT#8440
Merge branch '1.9.x' of ssh://github.com/chamilo/chamilo-lms into chamilo19