Serialize LVType to strings rather than integers.

[smoser]

Previously, serializing a LVType gave the helpful 0 or 1. This turns those into more useful values THICK, THIN, THINPOOL.

[codecov[bot]]

Codecov Report

Merging #49 into master will increase coverage by 0.36%. The diff coverage is 83.33%.

@@            Coverage Diff             @@
##           master      #49      +/-   ##
==========================================
+ Coverage   57.00%   57.37%   +0.36%     
==========================================
  Files          15       15              
  Lines        1584     1607      +23     
==========================================
+ Hits          903      922      +19     
- Misses        615      618       +3     
- Partials       66       67       +1     

Impacted Files	Coverage Δ
lvm.go	77.77% <83.33%> (+27.77%)	:arrow_up:

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[smoser]

@rchamarthy , Please review this wrt a few questions:

1. is it OK that I changed the values for constants THICK, THIN... ? It felt like the "unknown" should be 0, but that would definitely break anything that had old data.

2. @tych0 asked "why not just use strings" like:

   type LVType string
   const (
      THIN = LVType("THIN")
      THICK = LVType("THICK")
   )

[smoser]

I backed out the change in values, so that THICK is again 0. I opened up https://github.com/anuvu/disko/issues/50 to discuss/get feedback on strings.

Lets move that conversation there, and review this as it is.

[tych0]

sounds good, lgtm then.