text: Title: Call basic methods on `hparams` in a query 
  Body: ## 🚀 Feature : Call basic methods on `hparams` in a query ?
  Having tracked runs with aim I can query runs with a term like the following: 
  ```
  ( run.experiment == "AE_noisy" or run_experiment == "AE_smoothed" ) 
  ```
   This can be shortened to: `run.experiment.startwith("AE_")` 
  The same option for tracked hyperparameters, could be really usefull. So instead of having to run:
  ```
  ( run.hparams.optimizer == "ADAM or run.hparams.optimizer == "RADAM" )
  ``` 
  I'd wish to run 
  ```
  run.hparams.optimizer.endswith("ADAM")
  ```
  Currently this results in the error `query failed, 'Undefined' object is not callable`
  
  ### Motivation
  
  This would allow more flexible and shorter queries (especially when there are a lot of suffixes). Happy to hear any feedback whether this could be possible or is out of scope. Cheers!
  
  