Introduction of chart module

[pvgenuchten]

the chart module is hidden by default but opens when a user opens it
with it users should be able to create a chart of a selected layer (so it might be in the context menu of the layer, or in the query result panel)

extjs has a charting module which would fit perfectly on the extjs datastores
http://dev.sencha.com/deploy/ext-3.4.0/examples/#sample-6
however it requires flash

alternative might be highcharts