Handling of "maxfeatures limit reached" after a GetFeature request

As for now the "max number of results is reached" message is only displayed when the current grid (=layer) actually reaches this max number, not if the limit is hit combining all the grids/layers. In that case there is no tip telling that not all results have been returned.

This PR:
- adds a parameter to enable/disable the additional Mapserver request used to get the total number of hits of the previous WFS GetFeature request
- reworks the presentation of the "maximum number of features (200)" message => the number of features available in the grid is always displayed and the warning message is moved to the left near the total number of features (displayed only if the "enableTotalHits" param is set to true).
!

Here is an example screenshot:
[maxfeatures](https://cloud.githubusercontent.com/assets/1192331/3483173/f3476a64-038a-11e4-9e02-ab150ba24307.png)