Enhancement

1. Moved jump code from jmp_to_appcode to int main(), from sx107
2. Make code files compatible with GCC compiler, from tusker-tools
3. Disconnect USB device properly when exit bootloader, from tusker-tools

Bug fix

Try to fix the following issue: BUG for program size greater than 64K
(Seems it is caused by improper soft reset during parse ihex EOF inside the USB interrupt handler. The flash is already prog, but soft reset doesn't handle properly. Therefore, Windows reported the file is corrupt and stopped at 67%)

Support drag and drop the hex file, encryption mode

1. Support drag and drop the hex file to programming the board
2. Support encryption mode (AES256), can use hex_crypt utility to generate encrypted hex file
3. Tested on Windows 8, macOS Sierra and Ubuntu 18.04 only
4. Remove drag and drop the bin file since it is not working properly in macOS