Migration of jsx files to tsx 2 (#850)

This is to continue the work of migrating all the jsx files into tsx
files.
The MO is basically described here: #848.

About 7 files to go...

src/components/_SpecProperty.tsx

@@ -0,0 +1,46 @@
+import React from 'react'
+
+import SpecField, {SpecFieldProps} from './SpecField'
+import FunctionButtons from './_FunctionButtons'
+
+import labelFromFieldName from './_labelFromFieldName'
+
+
+type SpecPropertyProps = SpecFieldProps & {
+  onZoomClick(...args: unknown[]): unknown
+  onDataClick(...args: unknown[]): unknown
+  fieldName?: string
+  fieldType?: string
+  fieldSpec?: any
+  value?: any
+  errors?: unknown[]
+  onExpressionClick?(...args: unknown[]): unknown
+};
+
+
+export default class SpecProperty extends React.Component<SpecPropertyProps> {
+  static defaultProps = {
+    errors: {},
+  }
+
+  render() {
+    const {errors, fieldName, fieldType} = this.props;
+
+    const functionBtn = <FunctionButtons
+      fieldSpec={this.props.fieldSpec}
+      onZoomClick={this.props.onZoomClick}
+      onDataClick={this.props.onDataClick} 
+      onExpressionClick={this.props.onExpressionClick} 
+    />
+
+    const error = errors![fieldType+"."+fieldName as any] as any;
+
+    return <SpecField
+      {...this.props}
+      error={error}
+      fieldSpec={this.props.fieldSpec}
+      label={labelFromFieldName(this.props.fieldName || '')}
+      action={functionBtn}
+    />
+  }
+}