SettingsAccessor: Generialize error messages

The idea is to reuse this code elsewhere, so do not talk about
.user files.

Change-Id: I5db557a2c56b1eba2527b0cad2d1bdad4818ab8e
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
SettingsAccessor: Remove unnecessary check

We only save .user files, those are always environment specific

Change-Id: I230ebc769f0fba66546607888bbd8cca5b622a51
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
SettingsAccessor: Inline code from FileAccessor

Change-Id: I5243a1e7f38314ecd17a157e16b8cb6834a5b75c
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
SettingsAccessor: incrementVersion --> upgradeSettings

Also since incrementVersion is always called in a loop, move the loop
inside the function.

Change-Id: I6550a322b2423ed41f05c729b913647e52906cb9
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
SettingsAccessor: Add a QWidget *parent parameter to restoreSettings

Instead of hardcoding Core::ICore::mainWindow()

Change-Id: Iec7747945cbcb335ae552a0277a1527f598f1ff7
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
SettingsAccesor: Clean up includes

Change-Id: Ib800069148ed2790bb5f71b9ff42357ead642892
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
SettingsAccessor: Introduce SettingsAccessorPrivate

For now only hold m_writer and m_upgraders (which was m_handlers before)

Change-Id: If0baf99207e777f5d3349d32ef9ddee1b657f604
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
SettingsAccessor::SettingsData: Remove unused member m_usingBackup

Change-Id: I32f5a72900e5bd5446540cb139ff5c004216bde2
Reviewed-by: Daniel Teske <daniel.teske@digia.com>