While there's nothing grammatically wrong with "I am invited to the party", and I would understand what you intended to say, it's not the way a native speaker would phrase this. If I was discussing my invitation to a party that hasn't happened yet, I would say:
I've been invited to the party.
(I have sounds far too formal, so I've gone with the contraction I've here.)
As for your second example:
I was invited to the party.
I think you're correct that no implication of time is made here. The invitation clearly happened in the past, but the party could have been a week or a year ago, or later tonight, or two weeks from now (or even now!) Some possibilities:
I was invited to Mark's birthday party last year, but then they cancelled it at the last minute!
I was invited to the party next week, but I've got the kids that weekend so I might not be able to go.
Why do I have to leave? I was invited to this party! I have the invitation right here, see?
So while the invitation took place in the past, in this case I would say that the actual party could be at any time; context will make that clear.
This feature is added to the last version.
is not grammatical. It is not now being added, since the last version is already out there.
This feature is added to the current version.
This feature is added to this release.
These sentences still do sound a bit off though, you would normally find them as:
This feature has been added to the current version.
This feature has been / is being added to this release.
("is being" if the current release is still in development.)
For others than the current version:
This feature was added in the last version.
This feature will be added in the next version.
"Is added" is used to describe a change in functionality based on some action or event:
This feature is added when you upgrade to the newest version.
This feature is added by selecting the option in the "options" screen.
Best Answer
Strictly speaking I think this is probably a duplicate of Past tense for indicating long distance (a somewhat misleading title, since the OP is actually asking about the significance of the verb tense in, for example, "What is/was your name?").
The answer is that in almost all contexts, the verb tense in OP's example sentence has nothing to do with Past/Present. Native speakers frequently use "I was wondering..." instead of "I wonder...", because the past tense metaphorically "distances" the speaker from the utterance - which has the net effect of being more deferential, hesitant, polite, formal.
Partly for the same reason, and partly just because it sounds more "consistent", we often describe "the thing wondered about" in the past tense as well. Hence...
...but to most native speakers, #2 might often seem rather brusque, if not actually rude.