Improve behaviour of API search with context as the property

[BiyonFernando]

Purpose

Currently when doing exact search with context it is required to append version to the query. eg - context:"/test/1.0.0"
From this fix we will allow user to search all APIs which containing specified context. eg - context:"test"
Related issue - wso2/api-manager#3554

Approach

• Modify search query for exact search when the query parameter is context.
• This fix will preserve the original behaviour of this search. (eg - context:"/test/1.0.0")
• Search query as shown bellow when context:"test" is given.

eg - (*/test/* OR /test)