Files with duplicate names aren't handled properly

[boakley]

If you have two keyword files with the same filename (eg: feature1/keywords.robot, feature2/keywords.robot), rfhub only shows the keywords for one of the files.

There are two problems here:

1. we were doing an "insert or replace" when adding resource files, when we should be doing "insert"
2. the UI isn't designed to handle duplicate resource or library names.

item 1 is easy to fix; item 2 is a bit more gnarly.