Implement search mechanism

[vddesai1871]

Fixes #302

Checklist

• My branch is up-to-date with upstream/develop branch.
• Everything works and tested for Python 3.5.2 and above.

Description

Add searching mechanism to hydrus with help of IriTemplate.

Change logs

Added functions in helpers.py to generate IriTemplate for collections.
Added functions in crud.py to filter collections according to search parameters.

Search Example

It pretty much (or maybe completely) follows the procedure mentioned in the spec. To test it

1. Dereference any Collection endpoint(DroneCollection for example).
2. The response will contain IriTemplate attached to the search property.
3. The IriTemplate will have different IriTemplateMapping for each variable. You can use any combination of these variables to search the collection. (To name nested properties we follow a simple convention. They are represented as PropertyTitle[NestedPropertyTitle], so the variable to search drones by speed would be named as DroneState[Speed], the spec doesn't mention anything about it)

[vddesai1871]

Also, can you take a look at the path variable in the get_collection method (crud.py)? I think we can remove it.

[xadahiya]

According to resources.py path should never be None. Am I missing something? Can you please run a couple of tests and remove it if it's redundant?

[xadahiya]

@vddesai1871 Good to merge?

[vddesai1871]

Good to merge?

Yes, I pulled Hydra:Error changes and added an exception for handling invalid parameters. Now I think it's solid.

Changes done

[Mec-iS]

Do we have all the changes in python-hydra-core master?