[NSM GDrive] migrate to Util::MimeDetector (fix #1466)
[LHTR] Added enum for tab indices.
[LHTR] Only sync to HTML if current page is not HTML edit.

Fixes #1508.
[LHTR] Added basic HTML highlighter.
[LHTR] Added HTML attr name/value highlighting.
[LHTR] Instantiate highlighter.
[LHTR] Missing break.
[LHTR] Fixed tag ending.
[LHTR] Fixed parsing self-closing tags.
[Azoth] Close conf on /leave as well, fixes #1510.
[Azoth] Refactored DnD handling into ContactDropFilter.
[Azoth] Better image sending dialog.
[Popishu] Moved tab creation from Core.
[Popishu] Support recoverable tabs, closes #1478.
[Popishu] Use tab recover name for title on announcing.
[Popishu] Properly emit tabRecoverDataChanged() when needed.
[Popishu] Moved TabClass to Core.
[Popishu] Core shouldn't keep proxy.
[Popishu] Get rid of Core.
[Util] VkAuthManager::authCanceled() signal for #1511.