Python debugger source & display command (#1850)

Reworked source(src) command to display a given range of the code, defaults to 3.

Added display command which does the same as the source, except it displays the source code everytime a breakpoint is hit.

Made tests for display, extended tests for src.

JerryScript-DCO-1.0-Signed-off-by: Daniel Balla dballa@inf.u-szeged.hu

tests/debugger/do_src.expected

@@ -8,15 +8,12 @@ Stopped at breakpoint:1 tests/debugger/do_src.js:16 (in f() at line:15, col:1)
 Stopped at tests/debugger/do_src.js:20
 (jerry-debugger) s
 Stopped at <unknown>:1
-(jerry-debugger) src
-f = function f() {
-print('F2') }
+(jerry-debugger) source 0
+   1 > f = function f() {
 (jerry-debugger) n
 Stopped at tests/debugger/do_src.js:21
 (jerry-debugger) step
 Stopped at <unknown>:2 (in f() at line:1, col:5)
 (jerry-debugger) src
-f = function f() {
-print('F2') }
 (jerry-debugger) c
 Connection closed.