Implement the abstract class for stages.

[edyoshikun]

Similar to issue #166 and #167. The stages require an abstract class that should include the following:

-[ ] Get/Set position (already implemented but needs to be written in the abstract class)
-[ ] Get/Set relative position
-[ ] Get/Set maximium/miminum travel range
-[ ] Focus direction()?

We would probably need something for DAC controlled devices, but that is for a separate issue.

@AhmetCanSolak @yangjun9095 @ieivanov what do you think?

[AhmetCanSolak]

We can implement for software triggered stages at first. Do you have such devices @edyoshikun ?

[edyoshikun]

Sorry, I added the first prototoype to the abstract stage to the #162 PR. It should have been perhaps it's own PR. @AhmetCanSolak. I think the Thorlabs KCubes are a good example since we use them both in DaXi and mantis