Restructure layer settings for add modal

src/components/layers/LayerSourceBlock.jsx

@@ -0,0 +1,25 @@
+import React from 'react'
+
+import InputBlock from '../inputs/InputBlock'
+import StringInput from '../inputs/StringInput'
+import SelectInput from '../inputs/SelectInput'
+
+class LayerSourceBlock extends React.Component {
+  static propTypes = {
+    value: React.PropTypes.string.isRequired,
+    onChange: React.PropTypes.func.isRequired,
+    sourceIds: React.PropTypes.array.isRequired,
+  }
+
+  render() {
+    return <InputBlock label={"Source"}>
+      <SelectInput
+        value={this.props.value}
+        onChange={this.props.onChange}
+        options={this.props.sourceIds.map(s => [s, s])}
+      />
+    </InputBlock>
+  }
+}
+
+export default LayerSourceBlock