calculate number of graphs (connected segemts) if more than one -> connect them to get a fully networked system

Resolve "Bug: sparse_rail_generator might not generate an agent/target pair : Results in number of agents == 0."

Closes #176

See merge request flatland/flatland!185

#160 predictor documentation

Closes #160

See merge request flatland/flatland!184

#80 specifications as markdown moved from wiki

Closes #161, #159, and #79

See merge request flatland/flatland!182

#79 bugfix sphinx generated documentation #161 observation documentation  #159 documentation about new INFO