Revert "temporary return error hiding for master branch"

This reverts commit 8802912edc0f6bd482687639cd89d871bbfc4590.
Added STRICT_ERROR_MODE constant. If ==1 system will throw ErrorException on any error. Hard recommended for developers. Default is 0.
fix var
fix error handling in mass_mail4 function
code format
var fix
default val for second param in template->render()
add "in phpbt" checking in .php temlates
code format
upgrade works with PDO
upgrade: bump database version only if no errors while upgrade process
minor fix
text fix
update CHANGELOG