Fixing for bettrer copy and paste

1. To fix that copy and paste fails with blank cells.
2. To prevent to remove quote from a cell like
"=DROPDOWN(D3:D10)" (refer: cell b3 of /examples/inputs.html)
3. To accept un-matched quote like "hello
Limitation:
Where A1; "abc  and A2 = def", if you copy & paste A1:A2 to A3, A3
becomes abc\ndef, because A1:A2 and A3 have the same tsv equivalent;
"abc\ndef" .
Fix method for reading JSON

JSON's value is in text, so td.text should be used.
Now if a cell like
a<k
, it becomes only
a
after toTables.json.