Flash boot speedup GUI additions

[ZigiMigi]

Created a GUI for bootloader.

[themarpe]

Thanks @ZigiMigi !

Please open a PR to develop with GUI without the flash_boot_speedup changes in place.
This PR will then be merged after the GUI lands in develop, bringing in flash_boot_speedup changes with it.
(Because flash_boot_speedup PR won't be merged very soon yet, and to discuss the proposed changes separately)

Also, target this to utilities/device_manager.py and combine into one file

[ZigiMigi]

Hi,
alright I made a Develop PR.

[themarpe]

@ZigiMigi

Thanks - this PR should add new functionality that is added by flash_boot_speedup branch.

Namely:

• Boot header flashing (all types, with "fast boot", "gpio" and "usb" header flashing having a sane default along the configurability, and the rest can be more complex exposing various arguments to go along)
• Flash clear (flashClear - clears flashed application/pipeline)
• Raw memory reading / writing (via readCustom & writeCustom) - these should take in / or output a file and specify offset & size

Check the diff of the target branch's PR for functionality to expose: https://github.com/luxonis/depthai-python/pull/511/files

[ZigiMigi]

@themarpe
I brought this branch up to date (same as Develop branch)

• merged into 1 file and renamed
• all changes mentioned above were adressed
• your changes are also here