Additional validation and escaping for file names.

This adds additional front and backend validations for task order file
names. We are now restricting file names to a whitelist regex of
[A-Za-z0-9\-_ \.] for simplicity.

Note:
On the frontend, the filename string must have at least one character.
This is not true in the backend validation; because of the way the
entire task order form is validated, requiring input would break the
business logic currently implemented.

js/components/__tests__/upload_input.test.js

@@ -70,7 +70,7 @@ describe('UploadInput Test', () => {
     })
 
     const component = wrapper.find(uploadinput)
-    const event = { target: { value: '', files: [{ name: '' }] } }
+    const event = { target: { value: '', files: [{ name: 'sample.pdf' }] } }
 
     component.setMethods({
       getUploader: async () => new MockUploader('token', 'objectName'),