Add support for uploading and downloading.

New functions:
- Can upload target file.
- Can select target file from the uploaded ones.
- Can download the generated OTA file.
- Can monitor the stdout during OTA package generation.

Also decoupled the job running function with the web server code.

Test: Mannual tested.
Change-Id: Ic525ef3997f048d73b21ad1d9475d54b1f8d112c
12 files changed