Add support for file names searched containing relative path names.

For example, searching for "foo/bar/blah.txt" now returns all (known) files matching that relative path. The previous implementation would simply return no results, as we we only looking in the "name" part of filenames.
Fetch file system tree on tool window creation.

This ensures the tool window is up to date even if the file system tree is loaded before the tool window is created.
Tweak name search matching algorithm.

* Don't bother splitting words by spaces
* Match relative path names partially on each path component.
Experimenting with changing tree view icons dynamically.
Merge branch 'master' of https://github.com/rpaquay/vs-chromium

Conflicts:
	VsChromiumServer/Search/SearchEngine.cs
Improve TreeView icons.
Fix overflow display for file positions.
Better limit maximum amount of results for a search query.
Error on opening document at incorrect offset.
Upadte readme file.