Delete backup/restore functionality.

Reasons:

1) it's broken.
2) it doesn't back up everything.
3) the migration code is a nightmare to maintain and has been largely
ignored by developers when they add new features.
4) it may prompt some developers to create a better solution.  e.g. use
the parameter groups functionality in CF 1.13.0 and newer for backups.
parameter groups were specifically designed to be backed up and restored
by the FC and importantly, have version numbers in them.

Feel free to reference the code in this commit that was deleted for any
new system.

_locales/en/messages.json

@@ -38,24 +38,6 @@
         "message": "Device - <span style=\"color: #57a929\">Ready</span>"
     },
 
-    "backupFileIncompatible": {
-        "message": "Backup file provided was generated for previous version of the configurator and is incompatible with this version of configurator. Sorry"
-    },
-
-    "backupFileUnmigratable": {
-        "message": "Backup file provided was generated by a previous version of the configurator and is not migratable. Sorry."
-    },
-
-    "configMigrationFrom": {
-        "message": "Migrating configuration file generated by configurator: $1"
-    },
-    "configMigratedTo": {
-        "message": "Migrated configuration to configurator: $1"
-    },
-    "configMigrationSuccessful": {
-        "message": "Configuration migration complete, migrations applied: $1"
-    },
-
     "tabFirmwareFlasher": {
         "message": "Firmware Flasher"
     },
@@ -315,9 +297,6 @@
         "message": "<a href=\"http://webchat.freenode.net/?channels=cleanflight\" target=\"_blank\">Join via WebClient</a>"
     },
 
-    "initialSetupBackupAndRestoreApiVersion": {
-        "message": "<span style=\"color: red\">Backup and restore functionality disabled.</span>  You have firmware with API version <span style=\"color: red\">$1</span>, backup and restore requires <span style=\"color: #57a929\">$2</span>.  Please backup your settings via the CLI, see Cleanflight documentation for procedure."
-    },
     "initialSetupButtonCalibrateAccel": {
         "message": "Calibrate Accelerometer"
     },
@@ -336,21 +315,6 @@
     "initialSetupResetText": {
         "message": "Restore settings to <strong>default</strong>"
     },
-    "initialSetupButtonBackup": {
-        "message": "Backup"
-    },
-    "initialSetupButtonRestore": {
-        "message": "Restore"
-    },
-    "initialSetupBackupRestoreText": {
-        "message": "<strong>Backup</strong> your configuration in case of an accident, <strong>CLI</strong> settings are <span style=\"color: red\">not</span> included - See 'dump' cli command"
-    },
-    "initialSetupBackupSuccess": {
-        "message": "Backup saved <span style=\"color: #57a929\">successfully</span>"
-    },
-    "initialSetupRestoreSuccess": {
-        "message": "Configuration restored <span style=\"color: #57a929\">successfully</span>"
-    },
     "initialSetupButtonResetZaxis": {
         "message": "Reset Z axis, offset: 0 deg"
     },