Splitting Mesh into EnvironmentMesh and VehicleMesh

[thomaszwagerman]

Closes #78, closes #79, closes #80, closes #83, closes #91, closes #119, closes #155, closes #157

Summary of changes:

• Split instances of Mesh into EnvironmentMesh and VehicleMesh. Mesh has become an abstract class inherited by both.
• Route requests now require a Vehicle.
• Mesh ingestion has been adapted to dynamically recognise handle the ingestion of both EnvironmentMesh and VehicleMesh files. If a VehicleMesh is ingested, it will identify the Vehicle and check if it exists in the database, if not it will create it.
• select_mesh() updated to handle different types of meshes. In first instance search for a VehicleMesh that matches coordinates AND Vehicle. Should this not exists, then find an EnvironmentMesh within coordinates and create a VehicleMesh using supplied vehicle.
• optimise_route() is now a function which calls PolarRoute's optimisation functionality, not a task. Added add_vehicle_to_environment_mesh function. Task is replaced by a new create_and_calculate_route task which uses these functions to calculate optimal route using VehicleMesh, creating one if necessary.
• Tests have been adapted (and where appropriate, expanded) to accommodate these changes.
• Adds vehicle information to route response.
• Adds vehicle fixtures with SDA, Slocum and BoatyMcBoatFace.
• Vehicle created by fixture are prevented from being deleted.
• Enables battery-based vehicles to have their routes optimised for battery use.
• Changes the route response to return "energy" consumption instead of "fuel", to enable a consistent response for fuel-based and battery-based vehicles.
• Expands testing suite to cover mesh type ingestion and create_and_calculate_route tasks.
• PolarRoute 1.0.0 support, >= 1.1.8 required for custom vessel performance functionality.

TO DO:

• PolarRoute version release required, see Fix setuptools packages find, add vesselfactory to init PolarRoute#329
• New PolarRoute version incoporated in PolarRoute-pipeline, see Update PolarRoute version to enable custom vehicle functionality on meshes. PolarRoute-pipeline#17
• Upload compatible meshes to files.bas.ac.uk

[thomaszwagerman]

All required changes made and previous tests adapted to work, however test coverage is down to 76%.

Probably a bit of effort required in identifying where testing is now lacking with the introduction of a few new mechanics.

[thomaszwagerman]

Another round of SIIS integration improvements integrated