Add thing data chart activity

[hamsterready]

After tapping on resource name presented on thing details activity (#1) user shall see line or pie chart which represents latest data.

curl https://user:[email protected]/api/v1/thing/hYxUIwyTbE42ebT5wV7MFbqklO4=/timeseries/temp

and the output:

[ {
  "dataTimeMillis" : 1449315852706,
  "doubleValue" : 19.3840008,
  "stringValue" : null
}, {
  "dataTimeMillis" : 1449315818453,
  "doubleValue" : 15.3100004,
  "stringValue" : null
}, {
  "dataTimeMillis" : 1449315810766,
  "doubleValue" : 15.3100004,
  "stringValue" : null
}, {
  "dataTimeMillis" : 1449246281253,
  "doubleValue" : 15.3100004,
  "stringValue" : null
}, {
  "dataTimeMillis" : 1449137869912,
  "doubleValue" : 15.3100004,
  "stringValue" : null
}, {
  "dataTimeMillis" : 1449137858504,
  "doubleValue" : 15.3100004,
  "stringValue" : null
}, {
  "dataTimeMillis" : 1449137850919,
  "doubleValue" : 15.3100004,
  "stringValue" : null
} ]

Please note that the output may consists double-only values, string-only values or mix of both.

To deal with this kind of data we do the following:

1. If length of received list is > 0 then check first element and if doubleValue is not null then show line chart, otherwise if stringValue is not null show pie chart otherwise show generic screen saying "no data received yet".
2. For line charts - ignore all data points with doubleValue == null (or if library supports these create chart with gaps (web example: http://www.amcharts.com/demos/chart-with-gaps-in-data/)
3. For pie charts - iterate through the list, ignore elements with stringValue == null and aggregate to map by stringValue, for instance, list ["x", "x", "y", "x", "z"] -> {"x": 3, "y": 1, "z" : 1} - show pie chart.

[hamsterready]

CC @ktomek