Move all settings to c++

[PowerTuneDigital]

Bugfixes to save settings from existing users after update

[github-actions[bot]]

Here are the first 10 encountered errors:

appsettings.cpp(2): error cpplint: [build/include_subdir] Include the directory when naming header files [4]
appsettings.cpp(3): error cpplint: [build/include_order] Found C system header after other header. Should be: appsettings.h, c system, c++ system, other. [4]
appsettings.cpp(4): error cpplint: [build/include_order] Found C system header after other header. Should be: appsettings.h, c system, c++ system, other. [4]
appsettings.cpp(77): error cpplint: [whitespace/blank_line] Redundant blank line at the end of a code block should be deleted. [3]
appsettings.cpp(88): error cpplint: [whitespace/blank_line] Redundant blank line at the end of a code block should be deleted. [3]
appsettings.cpp(99): error cpplint: [whitespace/blank_line] Redundant blank line at the end of a code block should be deleted. [3]
appsettings.cpp(122): error cpplint: [whitespace/blank_line] Redundant blank line at the start of a code block should be deleted. [2]
appsettings.cpp(123): error cpplint: [whitespace/comments] Should have a space between // and comment [4]
appsettings.cpp(124): error cpplint: [whitespace/comments] Should have a space between // and comment [4]

Done processing appsettings.cpp Category 'build' errors found: 4 Category 'whitespace' errors found: 129 Total errors found: 133

[PowerTuneDigital]

Fix to keep settings of existing users