MDL-41213 theme_bootstrapbase: fixed license filemanager overflow

Conflicts:
	theme/bootstrapbase/style/moodle.css
MDL-39682 Forms, File Picker, Themes: Fix alignment of Form's Labels and Input elements in RTL mode (theme/clean)

Conflicts:
	theme/bootstrapbase/style/moodle.css
weekly release 2.5.1+
MDL-40631: Prevent students from submitting empty assignments.