Merge Filters from filters list with new HTML assistant [from #309]

[RealRaven2000]

When the user clicks the "merge filters" button, quickFilters 6.8 still uses the xhtml dialog:

this should use the new html dialog implemented in #309 when the switch in settings >> actions is set to use it:

the idea is to merge only selected items through the new assistant.

[RealRaven2000]

Test version below:

quickFilters-wx-6.8.1pre6.zip

---

To install the version above, download zip file and drag the file into Thunderbird Add-ons Manager (do not extract contents, it won't install like that)

[RealRaven2000]

Another version. I removed some code that disables [x] target Filter if an email is "Starred". I think we should still add the "move to" => target folder

quickFilters-wx-6.8.1pre8.zip

---

To install the version above, download zip file and drag the file into Thunderbird Add-ons Manager (do not extract contents, it won't install like that)