Updat the filter

* Do url pattern matching on the hostname
* Make the DomDocument saveHTML function compatible with older version
    of PHP 5
* Simplify the fetch_embed_code helper function
Update the TinyMCE plugin

* Simplify the course_id/type_id page logic
Update the local plugin files

* Reword/remove unncessary language strings
* Update the mediacore_media class:
** Base url decisions on the hostname
** Standardize formatting of function params & BOOL/NULL values
** Add some extra getters
* Update the locallib:
** Options html helper to show only LTI domains if mapped, or
   pubic link if no mappings
** Simplify tool ids helpers
Update the README with latest changes
Update version doc strings
Update local/ and filter/ version number to 1.6b