Update labels to use generic app name

[abbyad]

The following labels should be updated in the default build to match current naming, or to be more generic. Proposed label changes are noted below:

• https://github.com/medic/medic-android/blob/e5ae1b99e600ab22933fe6ae655aa0d611a940b4/src/main/res/values/strings.xml#L10

  • URL is not a valid instance

• https://github.com/medic/medic-android/blob/e5ae1b99e600ab22933fe6ae655aa0d611a940b4/src/main/res/values/strings.xml#L11

  • Application is not ready, please try again soon

• https://github.com/medic/medic-android/blob/e5ae1b99e600ab22933fe6ae655aa0d611a940b4/src/main/res/values/strings.xml#L40

  • Space is running low on this device. Application may not be able to start, or may perform strangely.

We can also leave it to each flavor to update them, but generic versions seem to work well.