CamFlasher with export/import file

Added ability to export and import files with CamFlasher. It is necessary to define a shared directory (see CamFlasher option menu), use "importer" command to copy files to the device, and "exporter" command to copy files to the computer. Copying is about 6 times faster than rshell. CamFlasher saves the position of the window, and allows you to change the font. A flash erase is required, otherwise the main.py produces an error on boot.