Add distinct notifications for new versus existing passes

[bsurd]

Notes:

• The message could be enhanced in this situation to be less confusing for a user as he already had the said passes and only use the x new version for when the passes are reset/he receives new passes each month.

Affected Platforms:

• Windows 10 (64-bit)
• Mac 10.14.2
• Linux Ubuntu 19.04

Affected versions:

• signed v17 build

Steps to reproduce

1. Log into SP with a user who has a limited version of the proxy.
2. Use one or multiple passes.
3. On a different machine log in with the same account.

Expected result

• The passes notification reads "You have x Firefox Private Network passes!" or "You have x Firefox Private Network passes remaining!"

Actual result:

• The passes notification reads "You have x new Firefox Private Network passes!".

[bakulf]

@betsymi what do you think about this issue?