tweaks to LoginTasks

I'd rather LoginTasks have no knowledge of m1/m2 instead relying on the displayStrings and siteConfig objects to determine behaviour.

I've tweaked the init method for LoginTasks so that all lookups for share my local home dir occur here (althought I'd rather pass it as a boolean to the init method)

I've also included a couple of subroutines which are not used on this branch relaying to saving a file to share your desktop session. I'd like them in master so that LoginTasks is the same on both branches, and its only launcher.py that diverergs (i.e. a view class, thus bug fixes to the controler logic on master will carry over to onetab)

Anyway, have a look, let me know what you think. I think these are low enough risk to incorporate into master, but maybe I'm kidding myself.