Improvements for PathStore

[Kianoosh76]

Here are a couple of improvements and debuggings for pathstore:

1. A gitignore file on the root folder was missing as files like local-input or iml files were not ignored.
2. When adding the view table, the partition and clustering keys should be added in the same order as the original table
3. Select statements are augmented with Pathstore-specific columns, so that users will be able to fetch custom columns (e.g., select a, b, c from ...) rather than just selecting everything (select * from ...)