Switch to libarchive and camera autodetect between splashes and themes (#142)

* switch to libarchive and get rid of minizip, introduce zip_memory_to_buf

* automatically detect whether the downloaded zip is a splash or a theme

* slightly simpler way

include/camera.h

@@ -41,7 +41,7 @@ typedef struct {
     struct quirc* context;
 } qr_data;
 
-bool init_qr(EntryMode current_mode);
+bool init_qr(void);
 void exit_qr(qr_data *data);
 void take_picture(void);