Support other decimal point symbols

[Regex](http://www.debuggex.com/r/Vs27p2kr5hNMALKs) to support comma "," and raised period "·" as decimal point symbols for TYPE_NUMERIC.

http://mathworld.wolfram.com/DecimalPoint.html
https://en.wikipedia.org/wiki/Decimal#Decimal_fractions

This is very important when reading HTML and writing to Excel.