Add change range key bindings for auto highlight symbols

Very useful to edit a symbol inside a function
Remove unused macro in init-auto-highlight-symbol
Add key bindings in auto-highlight-symbol micro state

c to change range
e to edit
Update auto highlight section in readme
Update goals in readme
Update main principles section in readme
Replace the concept of mini-mode by the concept of micro-state

In order to avoid confusion with Emacs minor modes.
Update TOC of readme