#915174 by sdboyer, sun: Remove pointless files[] declarations on files that are not declaring classes.

- Patch #561226 by fago, effulgentsia, sun, YesCT, marcingy: orms (elements) need to able to specify include files to be loaded for building.

#242962 by Heine: Add a 'tablesort' Form API element to unify various places we use a big table with JS-enabled checkboxes next to each item (with tests).