Build REST compliant API

[ambud]

REST API needed to delete tags from Tag Index so that storage space can be freed up.

• Validate REST APIs and their form
• Missing APIs for metadata, retention at the database, measurement and time series
• Create rename APIs are database and measurement
• Add unit tests for REST API, refer: QA Tests
• Create Swagger API docs

Currently the following APIs are supported:

    DELETE  /databases (com.srotya.sidewinder.core.api.DatabaseOpsApi)
    GET     /databases (com.srotya.sidewinder.core.api.DatabaseOpsApi)
    DELETE  /databases/{dbName} (com.srotya.sidewinder.core.api.DatabaseOpsApi)
    GET     /databases/{dbName} (com.srotya.sidewinder.core.api.DatabaseOpsApi)
    PUT     /databases/{dbName} (com.srotya.sidewinder.core.api.DatabaseOpsApi)
    GET     /databases/{dbName}/check (com.srotya.sidewinder.core.api.DatabaseOpsApi)
    DELETE  /databases/{dbName}/measurements/{measurementName} (com.srotya.sidewinder.core.api.MeasurementOpsApi)
    GET     /databases/{dbName}/measurements/{measurementName} (com.srotya.sidewinder.core.api.MeasurementOpsApi)
    PUT     /databases/{dbName}/measurements/{measurementName} (com.srotya.sidewinder.core.api.MeasurementOpsApi)
    GET     /databases/{dbName}/measurements/{measurementName}/check (com.srotya.sidewinder.core.api.MeasurementOpsApi)
    GET     /databases/{dbName}/measurements/{measurementName}/fields (com.srotya.sidewinder.core.api.MeasurementOpsApi)
    GET     /databases/{dbName}/measurements/{measurementName}/fields/{value} (com.srotya.sidewinder.core.api.MeasurementOpsApi)
    PUT     /databases/{dbName}/measurements/{measurementName}/series (com.srotya.sidewinder.core.api.MeasurementOpsApi)
    GET     /databases/{dbName}/measurements/{measurementName}/series/count (com.srotya.sidewinder.core.api.MeasurementOpsApi)
    PUT     /databases/{dbName}/measurements/{measurementName}/series/retention/{retentionPolicy} (com.srotya.sidewinder.core.api.MeasurementOpsApi)
    POST    /databases/{dbName}/query (com.srotya.sidewinder.core.api.DatabaseOpsApi)
    POST    /influx (com.srotya.sidewinder.core.api.InfluxApi)
    POST    /sql/database/{dbName} (com.srotya.sidewinder.core.api.SqlApi)