…TION` check

### What's done:

 * This commit adds a separate `extendedIndentForExpressionBodies` flag,
   defaulting to `false`.
 * The flag controls whether continuation indent is used to indent expression
   bodies (previously, controlled with `extendedIndentAfterOperators`).
 * The corresponding flags are:
   * _IDEA_: `CONTINUATION_INDENT_FOR_EXPRESSION_BODIES`
   * `.editorconfig`: `ij_kotlin_continuation_indent_for_expression_bodies`

### What's done:

 * `appendix.tex` changed.