Remove hardcoded 8928 datapoint limit

[pb66]

see https://community.openenergymonitor.org/t/feature-request-setting-for-data-point-limit/9922?u=pb66
https://community.openenergymonitor.org/t/request-datapoint-limit-until-8928-points/633/4?u=pb66
and https://openenergymonitor.org/forum-archive/node/12133.html)

Can we break this setting out into the settings.php?

[borpin]

Used

emoncms/Modules/feed/engine/CassandraEngine.php

Line 180 in a2a5ad8

if ($req_dp>8928) return array('success'=>false, 'message'=>"Request datapoint limit reached (8928), increase request interval or time range, requested datapoints = $req_dp");

emoncms/Modules/feed/engine/PHPTimeSeries.php

Line 235 in a2a5ad8

if ($req_dp>8928) return array("success"=>false, "message"=>"request datapoint limit reached (8928), increase request interval or time range, requested datapoints = $req_dp");

emoncms/Modules/feed/engine/PHPFina.php

Line 398 in a2a5ad8

if ($req_dp>8928) return array('success'=>false, 'message'=>"Request datapoint limit reached (8928), increase request interval or time range, requested datapoints = $req_dp");

[TrystanLea]

good idea, happy for this to be a setting, a user can assess the performance implication on their system