add begin(port) to esp8266webserver, move some strings to flash, some refactoring (#4148)

* add begin(port) to esp8266webserver, move some strings to flash, some refactoring

* Moved more strings to flash, unified some strings

* move mimetable strings into a standalone file

* more string moves to flash, remove duplicates, refactor of template method, minor styling

* Reverted moving small string to flash (no heap advantage, reduces bin size)

libraries/ESP8266WebServer/src/detail/mimetable.cpp

@@ -0,0 +1,35 @@
+#include "mimetable.h"
+#include "pgmspace.h"
+
+namespace mime
+{
+
+// Table of extension->MIME strings stored in PROGMEM, needs to be global due to GCC section typing rules
+const Entry mimeTable[maxType] ICACHE_RODATA_ATTR = 
+{
+    { ".html", "text/html" },
+    { ".htm", "text/html" },
+    { ".css", "text/css" },
+    { ".txt", "text/plain" },
+    { ".js", "application/javascript" },
+    { ".json", "application/json" },
+    { ".png", "image/png" },
+    { ".gif", "image/gif" },
+    { ".jpg", "image/jpeg" },
+    { ".ico", "image/x-icon" },
+    { ".svg", "image/svg+xml" },
+    { ".ttf", "application/x-font-ttf" },
+    { ".otf", "application/x-font-opentype" },
+    { ".woff", "application/font-woff" },
+    { ".woff2", "application/font-woff2" },
+    { ".eot", "application/vnd.ms-fontobject" },
+    { ".sfnt", "application/font-sfnt" },
+    { ".xml", "text/xml" },
+    { ".pdf", "application/pdf" },
+    { ".zip", "application/zip" },
+    { ".gz", "application/x-gzip" },
+    { ".appcache", "text/cache-manifest" },
+    { "", "application/octet-stream" } 
+};
+
+}