Naming and coding style convention, new linter tool. (#945)

* Makefile, Scripts: new linter
* About: remove ID from IC
* Firmware: remove double define for DIVC/DIVR
* Scripts: check folder names too. Docker: replace syntax check with make lint.
* Reformat Sources and Migrate to new file naming convention
* Docker: symlink clang-format-12 to clang-format
* Add coding style guide

applications/storage/filesystem_api.c

@@ -0,0 +1,38 @@
+#include "filesystem_api_defines.h"
+
+const char* filesystem_api_error_get_desc(FS_Error error_id) {
+    const char* result = "unknown error";
+    switch(error_id) {
+    case(FSE_OK):
+        result = "OK";
+        break;
+    case(FSE_NOT_READY):
+        result = "filesystem not ready";
+        break;
+    case(FSE_EXIST):
+        result = "file/dir already exist";
+        break;
+    case(FSE_NOT_EXIST):
+        result = "file/dir not exist";
+        break;
+    case(FSE_INVALID_PARAMETER):
+        result = "invalid parameter";
+        break;
+    case(FSE_DENIED):
+        result = "access denied";
+        break;
+    case(FSE_INVALID_NAME):
+        result = "invalid name/path";
+        break;
+    case(FSE_INTERNAL):
+        result = "internal error";
+        break;
+    case(FSE_NOT_IMPLEMENTED):
+        result = "function not implemented";
+        break;
+    case(FSE_ALREADY_OPEN):
+        result = "file is already open";
+        break;
+    }
+    return result;
+}