Increase verbosity of template compiling errors

[lekoder]

When compiling template fails, error message should contain data sufficient to pinpoint error (line and column at least, preferably snipplet).

[lekoder]

It seems there is no easy way to get error from main js parser:

http://stackoverflow.com/questions/35252731/find-details-of-syntaxerror-thrown-by-javascript-new-function-constructor

As alternative, I can implement syntax-checking for {{ }} tags directly in KTL. This should work, but done incorrectly can limit flexibility of tag.