Added Support for Origin

[phani2410]

This Commit takes care of parsing origin from xpath.

Also, it avoids the issue described in https://github.com/google/gnxi/issues/43

[codecov-io]

Codecov Report

Merging #51 into master will decrease coverage by 0.05%. The diff coverage is 50%.

@@            Coverage Diff             @@
##           master      #51      +/-   ##
==========================================
- Coverage   52.79%   52.74%   -0.06%     
==========================================
  Files          10       10              
  Lines        1197     1202       +5     
==========================================
+ Hits          632      634       +2     
- Misses        482      484       +2     
- Partials       83       84       +1

Impacted Files	Coverage Δ
utils/xpath/path.go	62.5% <50%> (-5.93%)	:arrow_down:

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