v0.5.2.2: Thunderbird 91 (and 102) support

Changes since v0.5.1:

Compatibility - Thunderbird 91 (and 102)

• #56: No longer failing to recurse subfolders in dupe search with TB 86 and later
• #55: No longer failing when trying to move messages to Trash with TB 91
• Other minor internal changes required for TB 91 compatibility
• Works with TB 102 as well

Other user-facing changes

• #67 Support for common-account Trash folder as the default move target (which is the default action for dupes)
• Review dialog title change.
• Bug fix: Email address stripping no longer fails when some characters need to be escaped.
• #119 Satisfying ATN requirement of setting an explicit maximum compatible version (103.0)

Internal

• #108 : Now failing more gracefully when some folders' messages cannot be iterated, rather than "crashing" the entire dupe search
• #65 : Dropped our own custom preference wrapper code in favor of using Preferences.jsm
• Dropped some internal checks relevant for unsupported, older TB versions.
• #66 : Discarded our custom isEmpty() implementation in favor of the same function from ObjectUtils.jsm
• Updated the extension loader ("Window Listener") API to v1.5.6.
• Build script changes.
• Dropped the string2hex facility - we no longer use it
• Removed any remaining traces of the "(alternative)" qualifier after the extension name.
• Removed mentions of Eyal's old email address in favor of his current one at GMX.
• Whitespace, indentation changes