Improving jquery.makeCollapsible:

Improving jquery.makeCollapsible:
* Setting toggle function in a variable to easier reuse it through the plugin
* Replace "-hide" and "-show" classes with "expanded" and "collapsed" respectively
* For more flexibility, if there's a toggle-element already, bind the function to it and use it instead. Otherwise, just create one as usual. See [[betawiki:User:Krinkle/CollapsingTestpageKr#footer|CollapsingTestpageKr#Combination example]]
** It's more likely that the source has a custom position of the togglelink waiting for it to be bound, then it to be already bound.
* Some comments improved
* Message key "hide" to "collapsible-collapse" (Follow-up r78915 CR)
* Message key "show" to "collapsible-expand"
* Changed toggle-link content filling from html() to text() (message errors like <keyname> caused an HTML-element to be created)