[New Feature] auto popup a new strings key panel if user enter a strings key that not exists.

[alexlee002]

If I enter a new strings key that not exists in current strings table, It would automatically (of if I cmd+Click the strings key) popup a panel that I can add a new strings key and multi-language values for it.

[alexlee002]

Or, if we write the strings value in source code like this:

NSLocalizedString(@"This is my strings value", tableName);

If the strings value "This is my strings value" is already existed in tableName.strings with a key @"my_key", we can popup a tip to tell the user to use the exists key instead. e.g.:

NSLocalizedString(@"my_key", tableName);

[nek023]

Thanks. So you have two ideas:

1. Add a new key-value pair from popup
2. Tell the users that the value is existing, and replace it with key if necessary

About the first one, I'd like to say this (in #47). And for the second one, I cannot imagine the use case...