Resolve "Access resources using pkg_resources and/or importlib_resources"

Closes #57

See merge request !57

#64 bugfix prediction should respect target

Closes #64

See merge request flatland/flatland!61

Merge branch 'master' of gitlab.aicrowd.com:flatland/flatland into 57-access-resources-through-importlib_resources

Merge branch 'master' of gitlab.aicrowd.com:flatland/flatland into 64-prediction-should-respect-target

Merge branch 'master' of gitlab.aicrowd.com:flatland/flatland into 64-prediction-should-respect-target

Moved Prediction from Env to Observation. You can now pass your own predictor to the tree observation builder. if no predictor is passed everything stays the same.

added get_many() method to observation builders, base class and derived. Also removed the render() methods in the env base class and railenv

Merge branch 'master' of gitlab.aicrowd.com:flatland/flatland into 57-access-resources-through-importlib_resources

Merge branch 'master' of gitlab.aicrowd.com:flatland/flatland into 57-access-resources-through-importlib_resources

Merge branch 'master' of gitlab.aicrowd.com:flatland/flatland into 57-access-resources-through-importlib_resources

fixed bug for treeobs in curved rails: now the tree branch will look as 'forward' even on a curve

See merge request flatland/flatland!59