Implement editing functionality

[dkocich]

Core functionality

• [x] editing system with the possibility to undo/redo all changes
• [x] add/remove tags to nodes/relations
• [x] change current tag (key/value/both) of nodes/relations

Tag editing view in sidebar

• [ ] LATER ~~~add some favorite tags or automcomplete to make tag editing quicker ng2-typeahead~~~

Upload modal window

• [x] preview all changes to user (partially done - upload modal with edits JSON)

Editing relations (other than tag editing)

• [x] Sorting of relations:
• [x] drag and drop (~~~OR up/down move buttons~~~) rows with each member - it should also create new change in the edit history
• [ ] LATER AND/OR button for automatic sort by geometry/connectivity between points, etc)

Tools to create new elements

• [x] nodes - stops / platforms
• it should prefill some attributes
• there should be some option to quickly select type of stop (bus, train, station, etc)
• [x] relations - routes and master relations (route_master's / stop_area's)

Verify if changeset can be uploaded on the production API

• [x] adding tags
• [x] removing tags
• [x] changing tags
• [x] reordering of members
• [x] creating elements (platforms currently)