Adding a filter and an if in javascript

1/ I added a filter to allow putting main code elsewhere than into the main plugin file. 
Using this filter your can provide to the updater the file where the actual root file of the plugin is (the file containing the comments describing the plugin).
Useful if like me, your plugin is split in several files and you don't want to call the updater in the main file.

2 / I corrected a javascript issue. I added a test before removing the two last characters of .plugin-version-author-uri html, because for me that was causing a wrong terminated link (cut a &lt;/a&gt; into &lt;/).
But I'm not very sure it still work as it is supposed to work, because I was unable to find a case the split should occur with my plugin, so I couldn't test it.