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/FieldCheckbox.tsx

@@ -0,0 +1,18 @@
+import React from 'react'
+import Block from './Block'
+import InputCheckbox, {InputCheckboxProps} from './InputCheckbox'
+
+
+type FieldCheckboxProps = InputCheckboxProps & {
+  label?: string;
+};
+
+
+export default class FieldCheckbox extends React.Component<FieldCheckboxProps> {
+  render() {
+    return <Block label={this.props.label}>
+      <InputCheckbox {...this.props} />
+    </Block>
+  }
+}
+