Factor out ol.source.Vector#addFeatureInternal
Add ol.source.Vector#addFeaturesInternal
Add ol.source.Vector#addFeatures
Use addFeaturesInternal in ol.source.Vector constructor
Change ol.source.Vector#removeFeatureInternal from private to protected
Clear null geometry features in ol.source.Vector#clear
Use addFeatures in ol.source.VectorFile
Merge pull request #1414 from twpayne/vector-api-add-features

[vector-api] Add ol.source.Vector#addFeatures
Set default canvas lineJoin and lineCap to 'round'
Merge pull request #1418 from fredj/vector-api-lineCap

[vector-api] Set default canvas lineJoin and lineCap to 'round'
Fix GeoServer format option param key

See http://docs.geoserver.org/latest/en/user/services/wms/vendor.html#format-options
Move serverType option to olx.source.ImageWMSOptions
Change serverType property type to string|undefined