Fix fatal error in PHP 5.2
Fix typo
Notice about missing non-unique column
Rewrite testcases for error handler

Now they actually test desired behaviour, not random side effects of the
code.
Fix class documentation
Wrap long lines
Merge pull request #154 from lem9/master

Notice about missing non-unique column
Update po files
Translated using Weblate (Czech)

Currently translated at 100.0% (2602 of 2602)
When referring to a table, we use the term "column"
Translated using Weblate (Dutch)

Currently translated at 100.0% (2601 of 2602)
Translated using Weblate (French)

Currently translated at 100.0% (2601 of 2602)
Merge remote-tracking branch 'origin/master'
Update po files
Merge remote-tracking branch 'origin/master'
Translated using Weblate (Dutch)

Currently translated at 100.0% (2602 of 2602)
Translated using Weblate (Czech)

Currently translated at 100.0% (2602 of 2602)
Translated using Weblate (Spanish)

Currently translated at 100.0% (2602 of 2602)
Translated using Weblate (Greek)

Currently translated at 100.0% (2602 of 2602)
Fix - Bugs:#3802 Datepicker displayed just the first time

Fixed the bug that was preventing the datepicker from displaying after
ajax call. datepicker remained initialized while its content was
replaced by the ajax response. tbl_change.js now reinitializes
datepicker everytime its loaded.