SPECTQL != string comparison support

[lievenjanssen]

Add != string comparison support in SPECTQL

Following url works:

http://data.irail.be/spectql/NMBS/Stations%7Bid,name-,longitude,latitude%7D?name==%27Ghent%20Dampoort%27:json

but following gives error:

data.irail.be/spectql/NMBS/Stations{id,name-,longitude,latitude}?name!='Ghent Dampoort':json

Error: Could not process this token: Parse Error: (NE)() not expected