Other changes include:
* Codebase: move JSON parsing logic from config.c/h to nxdt_json.c/h.
* Codebase: replace all calls to localtime() with localtime_r() to guarantee thread-safety.
* Codebase: updated todo.txt.
* utils: implement utilsParseGitHubReleaseJsonData(), utilsFreeGitHubReleaseJsonData(), utilsGetApplicationUpdatedState() and utilsGetApplicationUpdatedState().
* utils: add extra logic to move the application's NRO to its proper path if the launch path isn't the right one (commented out at this moment).
* utils: add extra logic to replace the application's NRO at exit (commented out at this moment).
* defines: add DEVOPTAB_SDMC_DEVICE and tweak GitHub URL macros.
* DownloadTask: set percentage to 0 if the download size is unknown.
* DownloadTask: fix ETA string formatting.
* OptionsTab: repurpose OptionsTabUpdateFileDialogContent into OptionsTabUpdateProgress.
* OptionsTab: implement OptionsTabUpdateApplicationFrame.
* RootView: move date formatting into the static GetFormattedDateString() method.
* Makefile: use _GNU_SOURCE as part of CFLAGS to use strptime().
