Add isTrainer and hasPowerMeter to activity interface

[thomaschampagne]

This PR adds ability to know if:

• An activity has been performed on a trainer: Usually everything performed with a fitness equipment, or anything virtual.

• An activity has been performed with a power meter (cycling, running, ...).

[codecov-io]

Codecov Report

Merging #44 into develop will increase coverage by 0.04%. The diff coverage is 75%.

@@             Coverage Diff             @@
##           develop      #44      +/-   ##
===========================================
+ Coverage    72.23%   72.27%   +0.04%     
===========================================
  Files          172      172              
  Lines         4340     4347       +7     
  Branches       645      645              
===========================================
+ Hits          3135     3142       +7     
  Misses        1190     1190              
  Partials        15       15

Impacted Files	Coverage Δ
src/activities/activity.ts	74.78% <75%> (+1.57%)	:arrow_up:

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