Fix strict notices for the Upload field. Closes #1753. Closes #1719.
updated legacy filtering of associated sections in entries table to make it consistent with the rest
fixed issue where associations drawer shows all entries from parent section when new entry is created and prepopulate parameter is given
fixed typo from last commit
fixed an issue where associations drawer throws fatal error when associated section has no visible or sortable fields in entries table
Merge pull request #1754 from jensscherbl/integration

Minor fixes around Associations
Fix Collapsible plugin on Symphony error pages. Allow {URL} to be evaluated as well as {SYMPHONY_URL} for the fatalerror.* templates.
Fix sloppy empty session check. This should fix the thousands of rows in the sym_sessions table
Whitespace & documentation tweak for Session fix
If a filter with an AND or OR operation contains no actual filtering value, then remove it from the filtering chain. Fixes #1759
Use General::getMimeType to determine uploaded file mimetype instead of relying on the browser. Fixes #1609
Release 2.3.3RC1
Don't assume associations are going to have prepopulation. Fixes #1761
Fix subheading for Datasources that aren't allowed to be edited in the DSE
Tracking Markdown 1.16
Fixes issue where the filter is dropped after changing the sort order on a filtered entries table.
Merge pull request #1763 from jensscherbl/bugfix

Filter is dropped after changing sort order on filtered entries table