fix the bug of appescaping about window not closing
make pointers to shell weak
check ptr to shell in platform event handlers
Fix 984: delete shell obj asap in force close case
support passing frame element to Window.showDevToolsJail()
add test case for #984
[manual testcase] Added test for issue #434
Merge pull request #1020 from richardcypher/nwinmem

[test]add case for #984
Merge pull request #1022 from alex-ter/nw-manual-test-#434

[manual testcase] Added test for issue #434
disable writing to debug.log by default

Fix #1031
bump version to 0.7.2
fix devtools launch crash