fix issue with creating SFC transitions using ST and IL

Beremiz generates text representation for transitions without names.
Therefore transition name in its IL code is not needed.

replace '-' with '.' in resource tab and transition/action SFC code


This makes tab names consistent with the way the same information is shown in variable panel.

check during program generation whether source signal is defined for single task

fix strange behavior on Backspace press in ST

Before:
if text was selected and cursor was at indention, one indention (two
spaces) was removed.

if cursor was at start position of the line, then nothing happened.

if cursor was in the middle of indention then on backspace more
indention were added


Now:
if text is selected, it will be removed.
if cursor is at start position, then new line will be removed.
if cursor was in the middle of indention one indention is removed.