MY_Lang: implement all MX_Lang parameters to fix E_STRICT notices

Strict standards: Declaration of MY_Lang::load() should be compatible with
CI_Lang::load
Strict standards: Declaration of MY_Lang::line() should be compatible with
CI_Lang::line

I did feel a bit guilty at the time, but I was having difficulty parsing
all the sludge.  But with the basics cleaned up, I'm happy to have another
go at piling on the hacks.  The code will be significantly less readable,
but at least I've commented the sort of things I was struggling to grok.
Template library: fix non-static method (E_STRICT notice)

All the other Template methods are static; this one needs to be as well.

"Strict standards: Non-static method Template::find_file() should not be
called statically in /home/alan/php/Bonfire/bonfire/libraries/template.php
on line 857"... and 3 other places.
Context library: fix non-static methods (E_STRICT notice)

All the other Context methods are static; these two need to be as well.

"Strict standards: Non-static method Contexts::context_nav() should not be
called statically in
/home/alan/php/Bonfire/bonfire/modules/ui/libraries/contexts.php
on line 343"

"Strict standards: Non-static method Contexts::sort_actions() should not be
called statically in
/home/alan/php/Bonfire/bonfire/modules/ui/libraries/contexts.php
on line 432"