Standardize the organization of the main and submodules

[aerispaha]

Follow the convention used within pyswmm: support cleaner importing of the main classes, straighten out the config and definitions.

support these pattern:

from swmmio import Model, FloodReport, ComparisonReport, INPDiff, BuildInstructions

mymodel = Model('model.inp')
mymodel.draw(param, ...) #is there a better function word?
mymodel.conduits = modified_conduits #setters/getters to make changing a model more straightforward

#access global/config variables in a more obvious way
import swmmio 
swmmio.config.prj = 'epsg:2272'
swmmio.config.shapefile_directory = '/path/containing/shapefiles/for/basemap'

[aerispaha]

Coordinate reference information should be stored at the model object level instead of in a global config setting. For example:

mymodel = swmmio.Model('path/to/model.inp')
mymodel.crs = 'epsg:2272'

[aerispaha]

Getting and setting model data should be straightforward. A possible implementation could look like this:

model = swmmio.Model('path/to/model.inp')

# get dataframe of junctions section from inp file
juncs = model.inp.junctions

# change the datum 
juncs['Elevation'] = juncs['Elevation'] + 10
model.inp.junctions = juncs
model.save() #overwrite existing model or optionally set a new filename 

# get a geojson representation object of the conduits
model.inp.conduits.to_json()

# retrieve specific subset of columns of data from rpt and inp files (as available) 
model.conduits(data=['MaxDepth, MaxQ', 'geometry'])