[BH-000] Update Harmony 2.9.1 changelog

Update changelog after releasing Harmony 2.9.1.

[BH-2085] Commit Harmony database migration

Committed settings database migration
required for Harmony 2 Pro.

[BH-2092] Change onboarding auto power off time

* Changed automatic power off time for initial
on/off onboarding screen.
* Removed unused onboarding welcome window.
* Minor cleanups.

[BH-2091] Change maximum focus time to 120 minutes

Changed maximum focus time length from
60 to 120 minutes.

[BH-2090] Fix blink when disabling Power Nap

Fix of the issue that frontlight would
blink for a second after light clicking
to stop ringing Power Nap.

[BH-2088] Add build stage for BellHybridPro

* Added PR build stage for BellHybridPro.
* Changed naming of update and flash
packages for Pro config.

[BH-2084] Add new battery profile for fuel gauge

Added new battery profile configuration
to fuel gauge chip to support battery
of larger capacity that will be used
in Harmony 2 Pro version.

[BH-2085] Set lower minimum brightness for Pro version

* Added ENABLE_VERSION_PRO build flag that
selects different config for 2 Pro device.
* Reduced lowest brightness level for Pro 2
device.
* Changed the format in which brightness values
are stored in database - previously it was
stored as PWM percentage, now 1-10 scale
system level is used.

[BH-2085] Modify PWM driver to handle duty cycles <1%

Modified current PWM driver implementation
so that PWM module is able to generate
signals with duty cycle below 1%. This is
needed to reduce frontlight brightness
for Harmony 2 Pro version.

[BH-2086] Add 2 Pro version detection

Added logic required to detect
and properly display Harmony
2 Pro version in About section.

[BH-2048] Major Eink driver refactor

* Cleaned up BSP layer of Eink driver.
* Removed changing TCON config with
different refresh modes, used one set
of values for all modes instead.
* Moved coordinates transformation
routines to separate file.
* Minor fixes in 2bpp transformation
routine.
* Cleanups in lots of various
places.

[BH-2081] Fix crash for MP3s with missing Xing frame

Fix of the issue that playing large MP3
files with missing Xing frame would
result in crash due to minimp3
trying to compute metadata by analyzing
the entire file and running out of
heap memory.

[BH-000] Update Harmony 2.9.0 changelog

Update changelog after Harmony 2.9.0
release.

[BH-2079] Fix outdated forum link

Fix of the issue that link to
Mudita Forum displayed at the
end of What's New would lead
to 404 page.

[BH-2078] Fix crash upon receiving invalid timestamp

Fix of the issue that the device would
crash and never be able to boot up
again after receiving invalid timestamp
(e.g. -1).

[BH-2077] Lower backlight sentinel frequency

Lowered backlight sentinel frequency from
528MHz to 66MHz, what resulted in ~50%
current consumption reduction in cases
when the device is idle with light
turned on (e.g. bedside lamp).

[BH-2076] Fix timer interval overflow

Fix of the issue that SystemTimer interval
computation would overflow when trying to
set interval longer than 4,294,967ms.
That resulted in setting invalid timeout
value.

[BH-2068] Remove pre-1.9.0 What's New entries

Removed pre-1.9.0 entries from What's New
database, as they will never be shown
anyway.

[BH-2075] Add GET method to time sync endpoint

Added GET method returning current Harmony
time as a timestamp. This is needed by MC
to implement time synchronization
functionality.

[BH-2068] Update What's New database

Added 2.9.0-related entries to
What's New database.