Add Find all references

Close #341.

What it does?

 - [x] Show "Find Symbol Results" when users invoke "Find All References" from context menu or press Shift + F12
 - [x] Show different icons for symbol definitions and uses
 - [x] Show file names, locations and current line of the usages
 - [x] Highlight the symbol in current line (on "Find Symbol Results" window)
 - [x] Support "Go to Definition/Reference" by context menu or left click

How it works?

We get all symbol locations of current solutions and attach them to `pIVsNavInfo` field of the search criteria. A magic number is used for `dwCustom` to distinguish our find result action.
In the `IVsSimpleLibrary2.GetList2`, these results are returned to populate `Find Symbol Results` window.

Limitations

Symbols are not properly sorted unless we alter their text representations http://stackoverflow.com/questions/3803444/sort-order-of-result-for-find-all-references-in-visual-studio.