* Resolves#764
* Add libqrencode and qtsvg dependencies
* Ensure QR code remains square
* Auto-close QR code dialog when database is locked
* Add databaseLocked() Signal to databaseWidget
* Correct otpauth URI output in Totp::writeSettings(...)
* Create history-based merging that keeps older data in history instead of discarding or deleting it
* Extract merge logic into the Merger class
* Allows special merge behavior
* Improve handling of deletion and changes on groups
* Enable basic change tracking while merging
* Prevent unintended timestamp changes while merging
* Handle differences in timestamp precision
* Introduce comparison operators to allow for more sophisticated comparisons (ignore special properties, ...)
* Introduce Clock class to handle datetime across the app
Merge Strategies:
* Default (use inherited/fallback method)
* Duplicate (duplicate conflicting nodes, apply all deletions)
* KeepLocal (use local values, but apply all deletions)
* KeepRemote (use remote values, but apply all deletions)
* KeepNewer (merge history only)
* Synchronize (merge history, newest value stays on top, apply all deletions)
* Eliminate TOTP logic from GUI elements
* Consolidate TOTP functionality under the Totp namespace
* Eliminate guessing about state and encoders
* Increased test cases
* Add entry view column for TOTP [#2132]
* General code cleanup, reduction of unnecessary steps, separation of concerns
* Rename SetupTotpDialog to TotpSetupDialog for consistency
* Add the concept of custom TOTP encoders, each with potential for custom
code alphabet, length, step interval and code direction (i.e. reversed)
* Select custom encoder via overload of the digits field of a loaded entry
* Allow selection of custom encoders via the "TOTP Settings" field's
size, as currently done by KeeTrayTOTP for Steam. Use "S" for the
short name of the Steam custom encoder
* Allow selection of custom encoders via the "otp" field by appending
a "&encoder=<name>" field to the URL query. For example,
"&encoder=steam"
* Update TOTP set-up dialog to permit selection between (default,
steam, custom) settings.
