[EGD-4712] Change quickstart.md to reflect current project state

Quickstart documentation was a bit out-of-date, thus containing some
minor inaccuracies. Also document didn't actually reflect desired
sequence of user actions.

[EGD-5086] Change audio device switching logic

Upon hardware change event, audio profile had been switched multiple
times forcing redundant initializations of all related objects. Logic
has been optimized and prepared for further refactor. Now upon hardware
event objects are initialized exactly once.

[EGD-4973] Fix absent notifications on home screen

SMS and Calls notifications require default init
of respective data base. Displaying notifications
require wider space reservation for some digits
(e.g. `8`)

[EGD-4920] Add API to get current operator name

Asynchronous API to get operator name,
also possibility to easy extend solution for
current operator technology and information about
operator selection mode (automatic/hand).

[EGD-4919] Add API functionality to set operator

Functionality for set operator (with name) and
set autoselect were added.

[EGD-4628] Add APN settings and URC handler for PDP context

Classes supporting APN settings on modem and telephone
configuration (synchronization) have been constructed.
Possibility of asynchronous execution
of individual actions via ServiceCellularAPI.
Added message with information about deactivation of the
PDP context (URC) that the
application / service can listen on.

[EGD-5133] Fix settings bus add duplications

Changed Bus Channels vector to set to prevent
duplicates and cleaned logging.

[EGD-4968] Change GUI service to optimize flow and memory management

Gui and Eink services refactor.
Displaying frames performance optimization.
Critical resources management.

[EGD-5026] Change Eink service code structure

Refactor.

[EGD-5099] Fix GUI module readme

Fixed typos in GUI module readme file.

[EGD-5151] Fix timers callback issue

Fix timers callbacked issue and make sure there is no need to
call connect() after each stop().

[EGD-5092] Add instructions to development_workflow

Added instructions regarding adding licenses of 3rd party code when
creating a PR.

[EGD-5092] Fix year to 2021

Updated the year to the current one.

[EGD-5092] Add 3rd party licenses

Added missing 3rd party licenses to relevant sections in
LICENSE.md

[EGD-5103] Fix year in license header check

Bumped year to 2021 in automated license header checker.

[EGD-5078] Fix Debug UART conditional enabling

Uart debug will be enabled only when redirecting logs to Uart

[EGD-4881] Add oscillator clock switching mechanisms

Osc will change automatically at the lowest CPU frequency,
which will save power

[DW-31] Add a condition that prohibits checks to be run on draft PRs

Unfortunately, github actions doesn't support using "if" property in
defaults and that's why we need to repeat it for all jobs

[EGD-4590] Change KBD parser to JSON for input keyboard files

Changed keyboard input language parser to parse JSON files.
Removed all KPROF files and added JSON.
Added unit tests for new parser.
Modified document about adding languages.

[EGD-5050] Add brownout detection

Brownout detectection realized through charger driver