[MOS-930] Fix for for misunderstanding holes in sms conversations

Not all messages can fit on the current screen in sms conversation windows,
so there may be some holes that might suggest that  there are no more messages
to display. Now, when therea are more SMS to see by scrolling up,
the Old Messages label will indicate this fact.

[MOS-1002] Change USSD code handling to match design

Fixed issues with GUI behaviour on failed
USSD code handling.
Minor code cleanup in several parts of system.

[BH-1733] Add Harmony version information

In the Settings->About section, we will have information
about which version of Harmony the user has.

co-author @Lefucjusz

[CP-1962] Add Harmony color detection

* Added serial number based Harmony color
detection.
* Unified serial number handling for both
products.

[BH-1690] Add information about the connection to the PC

Added text with information about the connection to the main window
when the USB cable is connected to the PC

[CP-1966] Deleted file which is played does not stop the playback timer

Fixed the timer issue when file was deleted during playback.

[MOS-578] Fix misleading SMS notification text

Display "New message", translated accordingly - in
singular - in case there had been multiple unread
SMS messages and now only one remains unread.

[MOS-933] Added translations for Bluetooth connection status

Ditto

[MOS-000] Cleanup of translation files

Removed unused, duplicated entries
Sorted up jsons

[CP-1852] Too many user files removes default relaxation audio from the list

Changed order in which files in Relaxation are displayed
Added error message when files limit is exceeded

[MOS-636] Added MMI/USSD confirmation

USSD/MMI codes are now confirmed after they are sended.

[BH-1639] Add welcome message with charging info

Add new bell welcome window
Add new close reasons
Add new actions
Bump assets version
Remove bold text from welcome message
Remove bold text from onboarding popups

[CP-1836] Lack of error handling for audio playback

Added error handling for incorrect audio formats and corrupted files inside Relaxation app

[MOS-874] Complement French translations

Additionally, deleted an unused translation item from
all languages.

[CP-1831] Editing contact which is deleted via Center can still be saved but with incomplete data

Fix for editing contact when it was deleted via Center.
Edited contact cannot be saved if it was deleted earlier. Proper communication is shown.
Fix for phonebook app was not handling database notifications correctly.

[MOS-166] Unify grey color levels

Unified gray color levels used for texts
displayed in GUI.
Fixed issue with 'No calls yet.' text
not displaying.

[MOS-901] Missing translation for words "show" and "replace"

Fix for missing translation for words "show" and "replace" in all
languages except for English.

[MOS-77] Notifications on the home screen shouldn't be bolded

Fix for bolded notification text in every language.

[MOS-663] Replacement for empty templates screen

Now there's information displayed that there are no
templates and in order to add some, the user needs
to use Mudita Center. Also, given no templates, the
screen doesn't show the 'USE' button.

[MOS-893] Fix invalid time description in the SMS thread

The sending/receiving time information will be displayed as follows:
- Only an hour –> for today
- Yesterday and hour –> for messages received/sent yesterday
- Day of the week and hour –> for messages received/sent within
last 7 days
- Date (day+month) and hour –> for messages older than week,
but still from the same year
- Date (day+month+year) and hour –> for messages
rom previous years