Make SmartTemplate⁴ compatible with the current Thunderbird beta (69) in
order to prepare for the next ESR release in October 2019.

For back-porting, I created a new GitHub branch at 
https://github.com/RealRaven2000/SmartTemplate4/tree/Tb52

To Do:
Use new preferences system. (See
https://developer.thunderbird.net/add-ons/upgrading-add-ons-for-tb68/list-of-changes-in-thunderbird-core#less-than-prefwindow-greater-than-less-than-prefpane-greater-than-less-than-preferences-greater-than-and-less-than-preference-greater-than)
Replace prefwindows with dialogs 
Replace groupbox elements with html fieldsets
Replace AddonManager (which is now a promise)
Replace document.createElement with createXULElement

Created an attachment (id=8630) [details]
2.1 pre 192

Here is a first preview that at least doesn't make (current) Thunderbird 69
crash. However, the document ready event of the composer window doesn't fire
reliably so it doesn't really work yet and I need to figure out why the changes
in templates are not saved from the preferences dialog. The later I will figure
out fairly soon, the composer issues are a little more tricky.

Created an attachment (id=8640) [details]
2.1 pre 244

Tested in Thunderbird 68.0 beta2.
# fixes to support new preferences system to make settings dialog work again,
especially on the multiline textboxes. In order to make instantApply /
automatic population of html:textarea work in Thunderbird 60, I needed to add
the attribute "preference-editable = "true"
# switched <html:fieldset> back to groupbox. 
  <html:legend> (formerly <caption>) is now replaced by 
<hbox class="groupbox-title">
  <label class="header">value</label>
</hbox>
# fixed groupbox sizing problems for template editing fields
# Improved spacings on SmartTemplate⁴ Pro tab
# Added Stationery Settings button
# Fixed composer startup code to be more reliable (removing setTimer)
# Avoid registering SmartTemplate4.stateListener multiple times
# only use document.createXULElement where it is available (Tb64 and above)
# New notificationbox system (xbl unbound)

Created an attachment (id=8646) [details]
2.1 pre 331

Fixed all ChromeUtil.Import statements to conform to new syntax

Improved matchTextFromBody: avoid scanning inserted quote header or anything
outside of the replied to email.

header.set.subject: Support quoting parts of Email body in subject line by
sanitizing newline / whitespace characters.

Added Standard License support.

Created an attachment (id=8647) [details]
2.1 pre 359 - final re

(From update of attachment 8647 [details])
Final build, with full locales

(From update of attachment 8647 [details])
Made obsolete by pre 359, which contains complete localisation

(From update of attachment 8646 [details])
made obsolete by pre359, which contains complete l10n

Resolved Complete - Release 2.1 - 28/07/2019