move Javascript from page.php to script.js

[mtmail]

Move Javascript into a separate file which helps with readability and can be used later to do separate testing or linting.

Small changes only:

• Fix one typo in index.php
• page.php write a data structure which script.js later reads. Example

<script type="text/javascript">
//<!--
    var init_l0_map = {"center":[30,0],"zoom":2,"force":false};
-->
</script>

• Use document.querySelector() instead of document.forms['f'].elements['comment'] to find DOM elements
• Use document.addEventListener() instead of L.DomEvent.on()

[Zverik]

Nice, I thought of doing it myself last week :)