(3) Add other options to find RichPaths in RichPathView

[AmrElmasry]

Add other ways to find RichPaths :

• findFirstRichPath() This can be useful if the vector has one path, so no need for searching by name and creating iterator for this.
• findRichPathByIndex(int index) This can be useful to find the paths in O(1) instead of O(n), This could be messy if the vector has many paths with complex structure, but it could be useful in cases like hamburger icon where the paths can be recognized easily by the index, This method returns null if the index out of bounds instead of throwing exception to match the existent findRichPathByName behavior.

I also updated couple of examples in the sample app to use them, and updated the code snippet in the readme file to include them.