Convert header menu to be API based to avoid it not being generated

[RealRaven2000]

Normally the SmartTemplates button on top of the email preview shows the reply and forward menus. I have seen this arbitrarily not filled with data, leading to an empty menu:

[RealRaven2000]

A current workaround for this is delaying the patch of the header area by increasing the value in

extensions.smartTemplate4.fileTemplates.menus.delayMessagePane

try 10000 (10 seconds) to start with

[RealRaven2000]

As an interim solution, I made the menu patching more stable by removing the injection code that is based on the menupopup ids (and inject an invisible <div> instead which contains the desired menu structure). I have also started writing test code for building the new menu via the API, which will be located on the test menu:

new version for testing, appears to be stable at the moment:

smartTemplate-fx-4.4pre94.zip

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To test the version above, download the zip file, drag the file into Thunderbird Add-ons Manager, do not extract contents or if won't install.

[RealRaven2000]

For the latest versions see #253, or use this one:

smartTemplate-fx-4.4pre144.zip