* 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.
