FAT on SPI Flash Library (#1809)

* First commit of FFat library

* Fixed reboot loops if no fat present. Added CMakeLists

* Functionalize the partition checks

* Cleanup, especially in format

* Dont format if mounted.  More wording cleanup

* 16M ffat should only be on 16M board

* Fix some casting issues that trip up the compiler when building as ESP-IDF component

libraries/FFat/src/FFat.h

@@ -0,0 +1,47 @@
+// Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+#ifndef _FFAT_H_
+#define _FFAT_H_
+
+#include "FS.h"
+#include "wear_levelling.h"
+
+#define FFAT_WIPE_QUICK 0
+#define FFAT_WIPE_FULL 1
+#define FFAT_PARTITION_LABEL "ffat"
+
+namespace fs
+{
+
+class F_Fat : public FS
+{
+public:
+    F_Fat(FSImplPtr impl);
+    bool begin(bool formatOnFail=false, const char * basePath="/ffat", uint8_t maxOpenFiles=10, const char * partitionLabel = (char*)FFAT_PARTITION_LABEL);
+    bool format(bool full_wipe = FFAT_WIPE_QUICK, char* partitionLabel = (char*)FFAT_PARTITION_LABEL);
+    size_t totalBytes();
+    size_t freeBytes();
+    void end();
+    bool exists(const char* path);
+    bool exists(const String& path);
+
+private:
+    wl_handle_t _wl_handle;
+};
+
+}
+
+extern fs::F_Fat FFat;
+
+#endif /* _FFAT_H_ */