Add configurable precision for measurements visible on channel list

[klew]

Currently EM shows numbers with 0.01 precission (i.e. 1013.14 kWh), while IC impulse counters (including energy) shows 0.1 precision (i.e. 1013.1 kWh or 540.2 m3).
In detail view for EM there is 0.001 precission, while for channels based on IC it shows only 0.01 precission.

Supla app should allow to configure precission (i.e. per function, or per individual channel) and this precission should be applied to both "list view" and "detail view".

There were also many requests to allow configuration of precission for thermometer channel.