Initial Implementation of batch slide loader

[akhil-rana]

Description

• A new batch slide loader app page has been created at /apps/batchloader/ to upload multiple files simultaneously with ease.
• Slide name can be generated by the user provided name eg. sample_1,sample_2 etc.
• File names can either be set to default (original file names) or can be generated similar to the slide name.
• This is an initial implementation and I look forward to suggestions and feedback.
• Working on better implementation of validation and error handling.
• Some functions in batchLoader.js are modified from chunked_loader.js and loader.js to behave accordingly since I was trying to solve the issue without making changes in slideLoader(at least for now).

Motivation and Context

**Why is this change required? What problem does it solve?

• In reference to Batch Slide Loader App #352

How Has This Been Tested?

• Tested on Mozilla 75.0, Chrome 81.0
• Ubuntu 19.10

Screenshots (if appropriate):

Please click on the gif to view in full screen if not visible clearly here.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[akhil-rana]

@birm
Am I heading in the right direction here?

[birm]

That's pretty cute! I'll review it more deeply in a bit.

[birm]

One little change for now; can we add a column which shows what the filename of the original file was?

[birm]

Actually, I'll approve this, as it's a reasonable initial implementation. I'll comment in the source issue for extending it. Thanks for the good work!

[akhil-rana]

Thank you.
I will be working on this to improve this more.