Some strings in Store application are not localized

[TanyaM]

Description:
There are few strings, tooltips here and there which have been missed in the localization effort.

Ex:
[1] https://github.com/wso2/carbon-apimgt/blob/6.x/features/apimgt/org.wso2.carbon.apimgt.store.feature/src/main/resources/store/site/themes/wso2/templates/menu/header/template.jag#L61
[2] https://github.com/wso2/carbon-apimgt/blob/6.x/features/apimgt/org.wso2.carbon.apimgt.store.feature/src/main/resources/store/site/themes/wso2/templates/api/api-listing-all/template.jag#L142
[3] https://github.com/wso2/carbon-apimgt/blob/6.x/features/apimgt/org.wso2.carbon.apimgt.store.feature/src/main/resources/store/site/themes/wso2/templates/menu/primary/template.jag#L10
[4] https://github.com/wso2/carbon-apimgt/blob/6.x/features/apimgt/org.wso2.carbon.apimgt.store.feature/src/main/resources/store/site/themes/wso2/templates/menu/primary/template.jag#L14

NOTE : Above list doesn't contain all.

Affected Product Version:
APIM 2.6.0

OS, DB, other environment details and versions:
Ubuntu 18.04, Chrome

Steps to reproduce:
Change the locale as described in the document https://docs.wso2.com/display/AM260/Adding+Internationalization+and+Localization to a different locate other than English.
Some strings will still be in English as they are not localized.