#1229 Add UI actions for chix/cifx/tooldefx files/editors, like for chi/cif/tooldef files/editors

• Best to review per commit.
• End-user visible changes:
  • All Chi, CIF and ToolDef tools now document that they can be started using .chix/.cifx/.tooldefx files.
  • All Chi, CIF and ToolDef UI actions are now supported on both .chi/.chix, .cif/.cifx, .tooldef/.tooldefx files
  • CIF event-based tools documentation now refers to 'CIF file' rather than '.cif file', when both .cif and .cifx are allowed, outside of selecting specific files/editors to start tools. It is sufficient to list the extensions in the specific sections about starting the tools.
  • Small improvements to Chi tool manual.

Closes #1229 (closed)