Merge branch 'market-beta' of https://github.com/particl/particl-desktop into listing_filtering

… listing template;

* re-works some extraneous method calls for conciseness and better readability;
* Adds a max file size for uploaded images (currently set at 2MB) - base64 encoding of large images (6+ MB) seems to cause a max stack call size failure for regex processing in html sanitization (my changes may have resulted in this, but another issue does exist for a possible resulting issue as well);
* Updates some of the template processing (when creating a new listing) to be promise-based instead of based on observables, to make clear the sequential processing of events and prevent excessive nested callback subscriptions processing.

…have been published).