Adding "limit" argument

[mohadelrezk]

From @mohadelrezk on December 2, 2016 11:7

In most of queries a LIMIT argument will help to handle bigger data sets.
Specially for (values) queries.

Copied from original issue: zeginis/JSON-QB-REST-API#6

[mohadelrezk]

From @zeginis on December 2, 2016 11:22

Yes indeed this is needed! We need to adopt a LIMIT strategy for all the queries

[zeginis]

Waiting for the API specification for details how to implement pagination

[mohadelrezk]

In README file limit is taged as optional for slice? query, but if not provided you get a null pointer exception error as follows:

HTTP ERROR 500
Problem accessing /slice. Reason:

Server Error

Caused by:

java.lang.NullPointerException
at org.certh.jsonqb.core.SPARQLresultTransformer.toObservationList(SPARQLresultTransformer.java:316)
at org.certh.jsonqb.core.CubeSPARQL.getSlice(CubeSPARQL.java:284)
at org.certh.jsonqb.api.impl.ImplRESTapi.getSlice(ImplRESTapi.java:374)