Centralize all exercises listing endpoints

Remove the endpoints Exercises.all and Exercises.suggested and
amplify the query limit of the Exercise.query_method, closes #78.
fixes position of .gitignore
Merge pull request #79 from AEHO/feat/server-config

Server config
Merge branch 'master' of github.com:AEHO/traintool
Add .gitignore

Add new .gitignore and ignore node_modules folder.