[FL-2491] File browser GUI module (#1237)

* File browser module and test app
* nfc: Add support for saved files in subdirectories
* nfc: Use helper function to get shadow path when loading data
* File browser dialog integration pt.1
* File browser dialog integration pt.2
* Gui,Dialogs: drop file select
* Correct use of dynamic string_t(string_ptr)

Co-authored-by: Yukai Li <yukaili.geek@gmail.com>
Co-authored-by: Aleksandr Kutuzov <alleteam@gmail.com>

applications/applications.mk

@@ -62,6 +62,7 @@ APP_USB_MOUSE = 1
 APP_BAD_USB = 1
 APP_U2F = 1
 APP_UART_ECHO = 1
+APP_FILE_BROWSER_TEST = 1
 endif
 
 
@@ -207,6 +208,11 @@ CFLAGS		+= -DAPP_KEYPAD_TEST
 SRV_GUI		= 1
 endif
 
+APP_FILE_BROWSER_TEST ?= 0
+ifeq ($(APP_FILE_BROWSER_TEST), 1)
+CFLAGS		+= -DAPP_FILE_BROWSER_TEST
+SRV_GUI = 1
+endif
 
 APP_ACCESSOR ?= 0
 ifeq ($(APP_ACCESSOR), 1)