Use identifier instead of identity

[AxelNennker]

What type of PR is this?

Add one of the following kinds:

• documentation

What this PR does / why we need it:

Use the term "identifier" if an identifier is talked about.

Operators often use the term "identity" when in fact it is an "identifier".
Generally an "identity" and an "identifier" are different.
There a several definitions for "identity" e.g. in OIDF, IETF and W3C e.g. "a collection of claims".
But identity is never used when an identifier is meant.

I think we should avoid operator-speak and use "identifier" if it is an "identifier".

[eric-murray]

IMEI really is defined as "International Mobile Equipment Identity". See TS 22.016.

Suggested change

	Mobile devices are allocated a unique identifier by the manufacturer, known as the International Mobile Equipment Identifier, or IMEI. The current software version (SV) of the device can be appended to this, in which case the identifier is known as the IMEI SV. This identifier is signalled to the mobile network when the device connects, both to confirm that the device is not blocked, and also allow device dependent network configurations to be implemented.
	Mobile devices are allocated a unique identifier by the manufacturer, known as the International Mobile Equipment Identity, or IMEI. The current software version (SV) of the device can be appended to this, in which case the identifier is known as the IMEI SV. This identifier is signalled to the mobile network when the device connects, both to confirm that the device is not blocked, and also allow device dependent network configurations to be implemented.

[eric-murray]

I'm generally happy with this, but IMEI really is "International Mobile Equipment Identity"