Add term size config

[haideriqbal]

This fixes: #810

Here hows the functionality has changed.

Anyone running their own instance of OLS can provide the param in application.properties. The value of param will be treated as upper limit on the number of rows fetched from solr. For example if the param value is 5000 then

• If no size param is defined in the URL then by default 5000 rows would be fetched in the API call
• If size param is specified in the URL e.g. 100 and the size is less than the value of config param then the 100 rows would be fetched
• If size param is specified in the URL e.g. 20000 and the size is greater than the value of config param then 5000 rows would be fetched.

In case of OLS, config param is optional and its default value is 1000.