CRUD operations for Admin interface

[igrigorov]

Create the following endpoints:

• [x] GET /l10n - returns all localization entries in format {id, locale, lic, value, active}
• [x] POST /l10n/entry - creates a new entry. Input in format {locale, lic, value}
• [x] PUT /l10n/entry/{id} - replaces the entry with id. Input in format {id, locale, lic, value, active}
  • Update ModifiedOn when updating to current timestamp
• [x] Integration Tests for all the above

[lambrospap]

PUT operation was changed in order to be updated with a given lic as discussed