Restore MHT support

[kkurt]

Latest version named unmht-8.3.2-an+fx+sm+tb.xpi for firefox seem to work, but the addon page tell you the is not compatible.
Righclick on the "add to firefox" link that appear to be disabled, save the xpi file the drag it to palemoon to install.
Save page or selections selection works fine; opening mht work too while it didn't work until the last update of mht and palemoon.
I'm still using unmht because of the "save selection" feature.

On another profile i have mozarchiver installed, looks like isn't working well with palemoon28 (the saved file contain gibberish) but i didn't tried anything yet for now (neither settings or check for new versions), so just ignore what i wrote if it does work for you.

edit:
Mozarchiver was saving incomplete pages without the layout, and when opening an existing mht (old or recent) it did open it as a text file.
Even if the version did not changed, uninstalling and reinstalling mozarchiver fixed everything and now seem to work like before; this may be a possible conflict with unmht that was uninstalled a while ago, but without reinstalling mozarchiver after removing unmht; or maybe is something else.