Add support for Lineage

• Added the following classes to support lineage retrieval
  • LineageRelation
  • DirectedPair
  • LineageGraph
  • LineageResponse
• Added the get_lineage method to AtlanClient
• Modify create_typdef in client to handle creating EnumDef
• Refresh caches on any SDK-driven creates or deletes

Fix problem with custom metadata creation

Fix problem where custom metadata created via the SDK failed to show up in the UI

Fix problem with custom metadata creation

Fix problem where custom metadata created via the SDK failed to show up in the UI

Add create method to Process asset

Merge pull request #44 from atlanhq/create_lineage

Add create method to Process class

Improve attachment of terms to assets

• Add remove_terms method to AtlanClient
• Add append_terms method to AtlanClient
• Add replace_terms method to AtlanClient

Simplify Readme Creation

Modify create method of the Readme asset to ease attaching Readme to assets.

Fix README.md

Fix broken link in README.md

Made changes to creating custom metadata

• Renamed get_business_attributes method get_custom_metadata in Referenceable.Attributes
• Renamed set_business_attributes method set_custom_metadata in Referenceable.Attributes
• Renamed BusinessAttributes to CustomMetadata
• Add parameter overwrite_custom_metadata to AtlanClient.upsert
• Add get_custom_metadata to CustomMetadataCache
• Update create functions

Update Create Methods

• Added create method to Column
• Updated Schema.create method to add schema to Database schemas collection
• Updated Table.create method to add table to Schema tables collection

Changes to improve usability

• Added relation_attributes parameter to IndexSearchRequest to specify the attributes to be included in each relationship that is included in the results of the search
• Set assets to empty list when no entities are returned by search
• Add classmethod ref_by_guid to Referencable
• Add classmethod ref_by_qualified_name to Referencable