add semicolon at the end of xor_scramble() declaration
implemented xor_scramble() function
refactor on_button_scramble() to use new xor_scrable_function
replace calls to m_Entry*.get_string() with get_text()
on_button_scramble(): fix filename to display in InfoBar
change xor_scrable() key parameter type to std::string
remove default arg from xor_scramble() implementation
remove 'separate encryption task'