Circle support and more options

ADDED: Circle Support

ADDED: You can now toggle global removal mode with map.pm.toggleGlobalRemovalMode() or via Toolbar
ADDED: you can now pass custom marker options for drawing markers (see Readme)
ADDED: you can now specify finishOnDoubleClick: true to complete the shape on dblclick.
IMPROVED: Better Controls/Toolbar functions, thanks @maxamante
FIXED: manually toggling global edit mode is now reflected in the toolbar state
FIXED: a few minor bugs