Merge pull request #62 from chamilo/1.9.x

1.9.x
remove 'overwrite' comment
Fixing user whoisonline preview.
Minor - fixing warnings.
Minor - removing whitespaces.
Minor - format code.
Allowing course order inside a session see BT#8316
Adding session duration feature see BT#8317
Minor - removing var_dumps.
Add optimization for user_rel_tag table (index) taken from campus.chamilo.org
Merge branch '1.9.x' of github.com:chamilo/chamilo-lms into 1.9.x
Minor - Fix warning in course description parsing
Allow admin users to use security key directly for WSCourseList webservice - refs BT#8268
Small update to SSO check to allow sso_referer not to include last path element to avoid issues with friendly URLs - refs BT#8268
Minor - Code styling changes (during #8268)
Add sso_challenge method as a second alternative to SSO authentication - refs BT#8268
Minor - Code styling changes (during #8268)
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