Optimize Point.lineProtocol()

[bentatham]

While testing high throughput, I profiled the sender, and discovered it was creating a new NumberFormat for every point, whether or not it actually ever needed it. I've changed it to use a ThreadLocal of it (since NumberFormat is not thread-safe), and to reuse the same instance. I've also changed it to use a single StringBuilder rather than returning strings (built by additional instances) and appending them together.

[codecov-io]

Codecov Report

Merging #336 into master will decrease coverage by 0.11%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master     #336      +/-   ##
============================================
- Coverage     79.33%   79.22%   -0.12%     
- Complexity      137      138       +1     
============================================
  Files            11       11              
  Lines           726      722       -4     
  Branches         79       78       -1     
============================================
- Hits            576      572       -4     
  Misses          109      109              
  Partials         41       41

Impacted Files	Coverage Δ	Complexity Δ
src/main/java/org/influxdb/dto/Point.java	82.87% <100%> (-0.46%)	25 <1> (+1)

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[majst01]

Hi,

i think this is duplicate of #330, which will be merged soon.

[bentatham]

lol -- so it is - nice to know that two of us got to some very similar optimizations independently.