file transfer - added protocol messages, handler functions, PICA_client API functions

git-svn-id: svn://localhost/project_picapica/trunk@299 fb96df88-216d-11de-830c-f3023f12d8ac
file sending and receiving, implemented required functions in PICA_client.c, support for bidirectional sending and receiving two files simultaneously, file operations (open, read, write) are handled inside PICA_client instead of caller functions

git-svn-id: svn://localhost/project_picapica/trunk@300 fb96df88-216d-11de-830c-f3023f12d8ac
use buffer on stack, removed old check buf == NULL

git-svn-id: svn://localhost/project_picapica/trunk@301 fb96df88-216d-11de-830c-f3023f12d8ac
fixed typo

git-svn-id: svn://localhost/project_picapica/trunk@302 fb96df88-216d-11de-830c-f3023f12d8ac