Write SQL projection parser consistent to ISO9075:2016

[fishroot]

From @fishroot on December 22, 2018 12:21

e.g. field_parse('x^2 as x2') == ('x', lambda x: x ** 2, 'x2')
or field_parse('sin(x+y) as sxy') == (('x', 'y'), lambda x, y: math.sin(x + y), 'sxy')

Copied from original issue: frootlab/rian#587