title: Return column per type in row bigQuery
body: <p>I want to return a row per timestamp with selected sensors, i.e.
  my data is loading like this:</p>
  
  <p>TIMESTAMP   SENSOR  TYPE    VALUE   </p>
  
  <p>2018-12-31 23:00:00 UTC
  WM0255
  mm
  731.424
  2<br>
  2018-12-31 23:00:00 UTC
  WM0212
  mm
  814.793
  3<br>
  2018-12-31 23:00:00 UTC
  WM0234
  mm
  265.607
  4<br>
  2018-12-31 23:00:00 UTC
  PM1110
  mm
  33.7823
  5<br>
  2018-12-31 23:00:00 UTC
  WM0231
  mm
  1467.69
  6<br>
  2018-12-31 23:00:00 UTC
  WM0244
  mm
  792.808
  7<br>
  2018-12-31 23:00:00 UTC
  WM0241
  mm
  339.997
  8<br>
  2018-12-31 23:00:00 UTC
  WH0034
  mm
  257.325
  9<br>
  2018-12-31 23:00:00 UTC
  WM0222
  mm
  805.086
  10<br>
  2018-12-31 23:00:00 UTC
  PM1114
  mm
  50.6498
  11<br>
  2018-12-31 23:00:00 UTC
  WH0038
  mm
  218.819
  12<br>
  2018-12-31 23:00:00 UTC
  WM0295
  mm
  175.98
  13<br>
  2018-12-31 23:00:00 UTC
  PM1108
  mm
  46.7903
  14<br>
  2018-12-31 23:00:00 UTC
  WM0239
  mm
  811.464
  15<br>
  2018-12-31 23:00:00 UTC
  PM1113
  mm
  48.81
  16<br>
  2018-12-31 23:00:00 UTC
  WM0236
  mm
  810.159
  17<br>
  2018-12-31 23:00:00 UTC
  WH0035
  mm
  152.784
  18<br>
  2018-12-31 23:00:00 UTC
  WM0223
  mm
  810.964
  19<br>
  2018-12-31 23:00:00 UTC
  WM0242
  mm
  1450.91
  20<br>
  2018-12-31 23:00:00 UTC
  WH0033
  mm
  295.649
  21<br>
  2018-12-31 23:00:00 UTC
  WM0245
  mm
  779.81
  22<br>
  2018-12-31 23:00:00 UTC
  WM0259
  mm
  793.539
  23<br>
  2018-12-31 23:00:00 UTC
  PM1104
  mm
  48.5385</p>
  
  <p>I want to return the values like this, where type is 'mm':</p>
  
  <p>TIMESTAMP WM0212 WM0255 WM0234</p>
  
  <p>2018-12-31 23:00:00 UTC x x x</p>
  
  <p>The reason is, I need one row per timestamp, but my data is not coming in at the same time.</p>