Support loading a new project filling a form

[willemarcel]

Currently, we support loading a project on the fly by passing the base image tile URL and the project classes names and colours in the URL params.

To make it easier to the user, we could have a form where the user would fill those details and DS Annotate would configure the URL params with the information the user provided.

[Rub21]

This functionality is been request a lot for trying the tool, People want to try the tool using their images, We could create a form the generate the url: like

classes=farm,00FFFF|tree,FF00FF
project=Farms_mapping
imagery_type=tms
imagery_url=https://gis.apfo.usda.gov/arcgis/rest/services/NAIP/USDA_CONUS_PRIME/ImageServer/tile/{z}/{y}/{x}?blankTile=false
project_bbox=-90.319317,38.482965,-90.247220,38.507418

And a result should be a URL:

http://devseed.com/ds-annotate?classes=farm,00FFFF|tree,FF00FF&project=Farms-mapping&imagery_type=tms&imagery_url=https://gis.apfo.usda.gov/arcgis/rest/services/NAIP/USDA_CONUS_PRIME/ImageServer/tile/{z}/{y}/{x}?blankTile=false&project_bbox=-90.319317,38.482965,-90.247220,38.507418

cc. @batpad @yunica