Interface data storage in PROGMEM (#71)

Adds a webpack plugin to package interface as PROGMEM into a header file in the framework.
Adds a build flag to optionally enable serving from PROGMEM or SPIFFS as required
Adds documentation changes to describe changes

lib/framework/SecuritySettingsService.h

@@ -4,6 +4,9 @@
 #include <AdminSettingsService.h>
 #include <SecurityManager.h>
 
+#define DEFAULT_ADMIN_USERNAME "admin"
+#define DEFAULT_GUEST_USERNAME "guest"
+
 #define SECURITY_SETTINGS_FILE "/config/securitySettings.json"
 #define SECURITY_SETTINGS_PATH "/rest/securitySettings"